diff --git a/bintree.c b/bintree.c
index 5cf82a9..75c5aac 100644
--- a/bintree.c
+++ b/bintree.c
@@ -2,35 +2,126 @@
 #include "stack.h"
 #include "bintree.h"
 
-//TODO: binären Suchbaum implementieren
-/*  * `addToTree`: fügt ein neues Element in den Baum ein (rekursiv),
-    * `clearTree`: gibt den gesamten Baum frei (rekursiv),
-    * `treeSize`: zählt die Knoten im Baum (rekursiv),
-    * `nextTreeData`: Traversierung mit Hilfe des zuvor implementierten Stacks. */
-
 // Adds a copy of data's pointer destination to the tree using compareFct for ordering. Accepts duplicates
 // if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
-TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate)
+TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize,
+                    CompareFctType compareFct, int *isDuplicate)
 {
+    if (data == NULL || compareFct == NULL)
+        return root;
 
+    if (root == NULL)
+    {
+        // neuer Knoten
+        TreeNode *node = malloc(sizeof(TreeNode));
+        if (node == NULL)
+            return NULL;
+
+        node->data = malloc(dataSize);
+        if (node->data == NULL)
+        {
+            free(node);
+            return NULL;
+        }
+        memcpy(node->data, data, dataSize);
+        node->left  = NULL;
+        node->right = NULL;
+
+        if (isDuplicate != NULL)
+            *isDuplicate = 0;
+
+        return node;
+    }
+
+    int cmp = compareFct(data, root->data);
+    if (cmp < 0)
+    {
+        root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
+    }
+    else if (cmp > 0)
+    {
+        root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
+    }
+    else
+    {
+        // Element bereits vorhanden
+        if (isDuplicate != NULL)
+        {
+            *isDuplicate = 1;
+            // Duplikate werden ignoriert
+        }
+        else
+        {
+            // Duplikate dürfen eingefügt werden -> wir hängen sie z.B. links an
+            root->left = addToTree(root->left, data, dataSize, compareFct, NULL);
+        }
+    }
+
+    return root;
 }
 
-// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
-// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first. On returning the next element,
-// push the top node and push all its left nodes.
+// Interner Stack für die Traversierung (strtok-ähnliches Verhalten)
+static StackNode *iterStack = NULL;
+
+// Hilfsfunktion: legt ab start alle linken Knoten auf den Stack
+static void pushLeftPath(TreeNode *start)
+{
+    while (start != NULL)
+    {
+        iterStack = push(iterStack, start);
+        start = start->left;
+    }
+}
+
+// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL,
+// the next entry of the last tree given is returned in ordering direction.
+// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first.
+// On returning the next element, push the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root)
 {
+    if (root != NULL)
+    {
+        // neue Traversierung starten: alten Stack aufräumen
+        if (iterStack != NULL)
+        {
+            clearStack(iterStack);
+            iterStack = NULL;
+        }
+        pushLeftPath(root);
+    }
 
+    if (iterStack == NULL)
+        return NULL;
+
+    // Nächsten Knoten holen
+    TreeNode *node = (TreeNode *)top(iterStack);
+    iterStack = pop(iterStack);
+
+    // rechten Teilbaum dieses Knotens auf den Stack bringen
+    if (node->right != NULL)
+        pushLeftPath(node->right);
+
+    return node->data;
 }
 
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root)
 {
+    if (root == NULL)
+        return;
 
+    clearTree(root->left);
+    clearTree(root->right);
+
+    free(root->data);
+    free(root);
 }
 
 // Returns the number of entries in the tree given by root.
 unsigned int treeSize(const TreeNode *root)
 {
+    if (root == NULL)
+        return 0;
 
-}
\ No newline at end of file
+    return 1u + treeSize(root->left) + treeSize(root->right);
+}
diff --git a/bintree.o b/bintree.o
new file mode 100644
index 0000000..e0d6dcc
Binary files /dev/null and b/bintree.o differ
diff --git a/doble.exe b/doble.exe
new file mode 100644
index 0000000..17251ed
Binary files /dev/null and b/doble.exe differ
diff --git a/doble_initial.exe b/doble_initial.exe
new file mode 100644
index 0000000..30f5ad3
Binary files /dev/null and b/doble_initial.exe differ
diff --git a/highscore.o b/highscore.o
new file mode 100644
index 0000000..e38d170
Binary files /dev/null and b/highscore.o differ
diff --git a/highscores.txt b/highscores.txt
index 4edd5a7..2e6dc4f 100644
--- a/highscores.txt
+++ b/highscores.txt
@@ -1 +1,3 @@
+Kilian;9927
+Kilian;4975
 player1;3999
diff --git a/main.o b/main.o
new file mode 100644
index 0000000..9b43f28
Binary files /dev/null and b/main.o differ
diff --git a/makefile b/makefile
index 1f15f75..1572893 100644
--- a/makefile
+++ b/makefile
@@ -1,4 +1,4 @@
-CC = gcc
+CC    = gcc
 FLAGS = -g -Wall -lm
 
 ifeq ($(OS),Windows_NT)
@@ -13,10 +13,18 @@ else
 endif
 
 raylibfolder = ./raylib
-unityfolder = ./unity
+unityfolder  = ./unity
 
 # --------------------------
-# Initiales Programm bauen (zum ausprobieren)
+# Phony Targets
+# --------------------------
+.PHONY: all doble doble_initial unitTests test_stack test_numbers clean vorbereitungen prepare
+
+# Standard-Target
+all: doble
+
+# --------------------------
+# Initiales Programm bauen (zum Ausprobieren)
 # --------------------------
 doble_initial:
 	$(CC) -o doble_initial $(BINARIES)/libdoble_complete.a
@@ -26,24 +34,66 @@ doble_initial:
 # --------------------------
 program_obj_files = stack.o bintree.o numbers.o timer.o highscore.o
 
-doble : main.o $(program_obj_files)
+doble: main.o $(program_obj_files)
 	$(CC) $(FLAGS) $^ -o doble
 
-$(program_obj_filesobj_files): %.o: %.c
-	$(CC) -c $(FLAGS) $^ -o $@
+# Generische Regel zum Bauen von .o aus .c
+%.o: %.c
+	$(CC) $(FLAGS) -c $< -o $@
+
+# Abhängigkeiten (optional, aber hilfreich für inkrementelles Bauen)
+main.o: main.c numbers.h stack.h bintree.h timer.h highscore.h
+numbers.o: numbers.c numbers.h bintree.h
+bintree.o: bintree.c bintree.h stack.h
+stack.o: stack.c stack.h
+timer.o: timer.c timer.h
+highscore.o: highscore.c highscore.h
+
+test_stack.o: test_stack.c stack.h
+test_numbers.o: test_numbers.c numbers.h bintree.h stack.h
 
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
-	echo "needs to be implemented"
+test_stack: test_stack.o stack.o
+	$(CC) $(FLAGS) $^ -o test_stack
+
+test_numbers: test_numbers.o numbers.o stack.o bintree.o
+	$(CC) $(FLAGS) $^ -o test_numbers
+
+unitTests: test_stack test_numbers
+	./test_stack
+	./test_numbers
+
+# --------------------------
+# Vorbereitungen zum Bauen des Programms
+# --------------------------
+vorbereitungen:
+	@echo "== Vorbereitungen zum Bauen des Programms =="
+	@echo "Prüfe benötigte Dateien..."
+	@test -f numbers.c   || (echo "FEHLT: numbers.c" && exit 1)
+	@test -f numbers.h   || (echo "FEHLT: numbers.h" && exit 1)
+	@test -f bintree.c   || (echo "FEHLT: bintree.c" && exit 1)
+	@test -f bintree.h   || (echo "FEHLT: bintree.h" && exit 1)
+	@test -f stack.c     || (echo "FEHLT: stack.c" && exit 1)
+	@test -f stack.h     || (echo "FEHLT: stack.h" && exit 1)
+	@test -f timer.c     || (echo "FEHLT: timer.c" && exit 1)
+	@test -f timer.h     || (echo "FEHLT: timer.h" && exit 1)
+	@test -f highscore.c || (echo "FEHLT: highscore.c" && exit 1)
+	@test -f highscore.h || (echo "FEHLT: highscore.h" && exit 1)
+	@test -f main.c      || (echo "FEHLT: main.c" && exit 1)
+	@echo "Alle Dateien vorhanden."
+	@echo "Vorbereitung abgeschlossen!"
+
+# englischer Alias
+prepare: vorbereitungen
 
 # --------------------------
 # Clean
 # --------------------------
 clean:
 ifeq ($(OS),Windows_NT)
-	del /f *.o doble
+	del /f *.o doble doble_initial test_stack test_numbers
 else
-	rm -f *.o doble
+	rm -f *.o doble doble_initial test_stack test_numbers
 endif
\ No newline at end of file
diff --git a/numbers.c b/numbers.c
index f59d9a2..f199fbe 100644
--- a/numbers.c
+++ b/numbers.c
@@ -5,22 +5,109 @@
 #include "numbers.h"
 #include "bintree.h"
 
-//TODO: getDuplicate und createNumbers implementieren
-/*  *   * Erzeugen eines Arrays mit der vom Nutzer eingegebenen Anzahl an Zufallszahlen.
-  * Sicherstellen, dass beim Befüllen keine Duplikate entstehen.
-  * Duplizieren eines zufälligen Eintrags im Array.
-  * in `getDuplicate()`: Sortieren des Arrays und Erkennen der doppelten Zahl durch Vergleich benachbarter Elemente. */
+// Hilfsfunktion für qsort und den Binärbaum: Vergleich von unsigned int
+static int compareUnsignedInt(const void *a, const void *b)
+{
+    const unsigned int *ua = (const unsigned int *)a;
+    const unsigned int *ub = (const unsigned int *)b;
+
+    if (*ua < *ub)
+        return -1;
+    else if (*ua > *ub)
+        return 1;
+    else
+        return 0;
+}
 
 // Returns len random numbers between 1 and 2x len in random order which are all different, except for two entries.
 // Returns NULL on errors. Use your implementation of the binary search tree to check for possible duplicates while
 // creating random numbers.
 unsigned int *createNumbers(unsigned int len)
 {
+    if (len < 2)
+        return NULL;
 
+    unsigned int *numbers = malloc(len * sizeof(unsigned int));
+    if (numbers == NULL)
+        return NULL;
+
+    // Zufall initialisieren
+    srand((unsigned int)time(NULL));
+
+    TreeNode *root = NULL;
+    unsigned int i = 0;
+
+    // len-1 verschiedene Zufallszahlen im Bereich [1, 2*len] erzeugen
+    while (i < len - 1)
+    {
+        unsigned int candidate = (unsigned int)(rand() % (2 * len)) + 1;
+        int isDuplicate = 0;
+
+        TreeNode *newRoot = addToTree(root, &candidate, sizeof(unsigned int),
+                                      compareUnsignedInt, &isDuplicate);
+        if (newRoot == NULL && root == NULL)
+        {
+            // Speicherfehler beim ersten Einfügen
+            clearTree(root);
+            free(numbers);
+            return NULL;
+        }
+        root = newRoot;
+
+        if (!isDuplicate)
+        {
+            numbers[i] = candidate;
+            ++i;
+        }
+        // bei Duplikat wird einfach eine neue Zufallszahl generiert
+    }
+
+    // Einen zufälligen Eintrag aus den ersten len-1 duplizieren
+    unsigned int duplicateIndex = (unsigned int)(rand() % (len - 1));
+    numbers[len - 1] = numbers[duplicateIndex];
+
+    // Baum wird nicht mehr benötigt
+    clearTree(root);
+
+    // Das Array durchmischen (Fisher-Yates-Shuffle), damit das Duplikat an zufälliger Position steht
+    for (unsigned int j = len - 1; j > 0; --j)
+    {
+        unsigned int k = (unsigned int)(rand() % (j + 1));
+        unsigned int tmp = numbers[j];
+        numbers[j] = numbers[k];
+        numbers[k] = tmp;
+    }
+
+    return numbers;
 }
 
 // Returns only the only number in numbers which is present twice. Returns zero on errors.
 unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
 {
+    if (numbers == NULL || len < 2)
+        return 0;
 
-}
\ No newline at end of file
+    // Kopie des Arrays anlegen, da qsort in-place sortiert
+    unsigned int *copy = malloc(len * sizeof(unsigned int));
+    if (copy == NULL)
+        return 0;
+
+    memcpy(copy, numbers, len * sizeof(unsigned int));
+
+    // Sortieren mit qsort
+    qsort(copy, len, sizeof(unsigned int), compareUnsignedInt);
+
+    // Benachbarte Elemente vergleichen, um das Duplikat zu finden
+    unsigned int duplicate = 0;
+    for (unsigned int i = 1; i < len; ++i)
+    {
+        if (copy[i] == copy[i - 1])
+        {
+            duplicate = copy[i];
+            break;
+        }
+    }
+
+    free(copy);
+    return duplicate; // 0 falls kein Duplikat gefunden (Fehlerfall)
+}
diff --git a/numbers.o b/numbers.o
new file mode 100644
index 0000000..c979e22
Binary files /dev/null and b/numbers.o differ
diff --git a/stack.c b/stack.c
index e3a90d4..9526218 100644
--- a/stack.c
+++ b/stack.c
@@ -1,33 +1,46 @@
 #include <stdlib.h>
 #include "stack.h"
 
-//TODO: grundlegende Stackfunktionen implementieren:
-/*  * `push`: legt ein Element oben auf den Stack,
-    * `pop`: entfernt das oberste Element,
-    * `top`: liefert das oberste Element zurück,
-    * `clearStack`: gibt den gesamten Speicher frei. */
-
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
+    StackNode *node = (StackNode *)malloc(sizeof(StackNode));
+    if (node == NULL)
+        return stack; // keine Änderung bei Speicherfehler
 
+    node->data = data;
+    node->next = stack;
+    return node;
 }
 
 // Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
+    if (stack == NULL)
+        return NULL;
 
+    StackNode *next = stack->next;
+    free(stack);
+    return next;
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
+    if (stack == NULL)
+        return NULL;
 
+    return stack->data;
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
-
-}
\ No newline at end of file
+    while (stack != NULL)
+    {
+        StackNode *next = stack->next;
+        free(stack);
+        stack = next;
+    }
+}
diff --git a/stack.h b/stack.h
index f7d542d..5230c6b 100644
--- a/stack.h
+++ b/stack.h
@@ -7,7 +7,12 @@ The latest element is taken from the stack. */
 
 #include <stdlib.h>
 
-//TODO: passenden Datentyp als struct anlegen
+// einfacher verketteter Stack
+typedef struct StackNode
+{
+    void *data;
+    struct StackNode *next;
+} StackNode;
 
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data);
@@ -23,3 +28,4 @@ void *top(StackNode *stack);
 void clearStack(StackNode *stack);
 
 #endif
+
diff --git a/stack.o b/stack.o
new file mode 100644
index 0000000..9951e86
Binary files /dev/null and b/stack.o differ
diff --git a/test_numbers.c b/test_numbers.c
new file mode 100644
index 0000000..84062e8
--- /dev/null
+++ b/test_numbers.c
@@ -0,0 +1,121 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include "numbers.h"
+
+/*
+ * Unit-Tests für createNumbers und getDuplicate:
+ *  - createNumbers liefert ein gültiges Array
+ *  - alle Zahlen liegen im Bereich [1, 2*len]
+ *  - genau eine Zahl kommt doppelt vor
+ *  - getDuplicate findet genau diese doppelte Zahl
+ *  - Fehlerfälle (NULL-Pointer, zu kleine Länge)
+ */
+
+static void check_numbers_array(unsigned int *numbers, unsigned int len)
+{
+    unsigned int maxValue = 2 * len;
+    unsigned int *counts;
+    unsigned int i;
+    unsigned int duplicatesCount = 0;
+
+    assert(numbers != NULL);
+
+    counts = (unsigned int *)calloc(maxValue + 1, sizeof(unsigned int));
+    assert(counts != NULL);
+
+    // Werte zählen und Bereich prüfen
+    for (i = 0; i < len; ++i)
+    {
+        unsigned int v = numbers[i];
+        assert(v >= 1 && v <= maxValue);
+        counts[v]++;
+    }
+
+    // Prüfen: genau eine Zahl kommt zweimal vor, alle anderen höchstens einmal
+    for (i = 1; i <= maxValue; ++i)
+    {
+        if (counts[i] == 2)
+            duplicatesCount++;
+        else
+            assert(counts[i] == 0 || counts[i] == 1);
+    }
+
+    assert(duplicatesCount == 1);
+
+    free(counts);
+}
+
+static void test_createNumbers_and_getDuplicate(unsigned int len)
+{
+    printf("test_createNumbers_and_getDuplicate(len=%u)...\n", len);
+
+    unsigned int *numbers = createNumbers(len);
+    assert(numbers != NULL);
+
+    // Arraystruktur überprüfen
+    check_numbers_array(numbers, len);
+
+    // Nochmal zählen, um das Duplikat zu kennen
+    unsigned int maxValue = 2 * len;
+    unsigned int *counts = (unsigned int *)calloc(maxValue + 1, sizeof(unsigned int));
+    assert(counts != NULL);
+
+    for (unsigned int i = 0; i < len; ++i)
+    {
+        unsigned int v = numbers[i];
+        counts[v]++;
+    }
+
+    unsigned int expectedDuplicate = 0;
+    for (unsigned int v = 1; v <= maxValue; ++v)
+    {
+        if (counts[v] == 2)
+        {
+            expectedDuplicate = v;
+            break;
+        }
+    }
+    assert(expectedDuplicate != 0);
+
+    // getDuplicate testen
+    unsigned int found = getDuplicate(numbers, len);
+    assert(found == expectedDuplicate);
+
+    free(counts);
+    free(numbers);
+
+    printf("...OK\n");
+}
+
+static void test_getDuplicate_error_cases(void)
+{
+    printf("test_getDuplicate_error_cases...\n");
+
+    // NULL-Array
+    unsigned int dup = getDuplicate(NULL, 10);
+    assert(dup == 0);
+
+    // Länge < 2
+    unsigned int dummy[1] = {42};
+    dup = getDuplicate(dummy, 1);
+    assert(dup == 0);
+
+    printf("...OK\n");
+}
+
+int main(void)
+{
+    printf("Running numbers unit tests...\n\n");
+
+    // Typische Testfälle mit verschiedenen Längen
+    test_createNumbers_and_getDuplicate(5);
+    test_createNumbers_and_getDuplicate(10);
+    test_createNumbers_and_getDuplicate(20);
+
+    // Fehlerfälle
+    test_getDuplicate_error_cases();
+
+    printf("\nAll numbers tests passed.\n");
+    return 0;
+}
\ No newline at end of file
diff --git a/test_numbers.exe b/test_numbers.exe
new file mode 100644
index 0000000..eddc46e
Binary files /dev/null and b/test_numbers.exe differ
diff --git a/test_numbers.o b/test_numbers.o
new file mode 100644
index 0000000..6d60ab7
Binary files /dev/null and b/test_numbers.o differ
diff --git a/test_stack.c b/test_stack.c
new file mode 100644
index 0000000..a1a7f27
--- /dev/null
+++ b/test_stack.c
@@ -0,0 +1,102 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include "stack.h"
+
+/* 
+ * Einfache Unit-Tests für den Stack:
+ *  - push/pop: LIFO-Verhalten
+ *  - top: richtiges Element
+ *  - Verhalten bei leerem Stack
+ */
+
+static void test_push_pop_lifo(void)
+{
+    printf("test_push_pop_lifo...\n");
+
+    StackNode *stack = NULL;
+
+    int a = 1;
+    int b = 2;
+    int c = 3;
+
+    stack = push(stack, &a);
+    stack = push(stack, &b);
+    stack = push(stack, &c);
+
+    // LIFO: zuerst c
+    assert(top(stack) == &c);
+    stack = pop(stack);
+
+    // dann b
+    assert(top(stack) == &b);
+    stack = pop(stack);
+
+    // dann a
+    assert(top(stack) == &a);
+    stack = pop(stack);
+
+    // jetzt leer
+    assert(stack == NULL);
+    assert(top(stack) == NULL);
+
+    printf("...OK\n");
+}
+
+static void test_empty_stack_operations(void)
+{
+    printf("test_empty_stack_operations...\n");
+
+    StackNode *stack = NULL;
+
+    // pop auf leerem Stack sollte einfach NULL liefern
+    stack = pop(stack);
+    assert(stack == NULL);
+
+    // top auf leerem Stack sollte NULL liefern
+    assert(top(stack) == NULL);
+
+    // clearStack auf leerem Stack darf nicht crashen
+    clearStack(stack);
+
+    printf("...OK\n");
+}
+
+static void test_clearStack(void)
+{
+    printf("test_clearStack...\n");
+
+    StackNode *stack = NULL;
+    int values[10];
+    int i;
+
+    // Wir legen 10 Elemente auf den Stack
+    for (i = 0; i < 10; ++i)
+    {
+        values[i] = i;
+        stack = push(stack, &values[i]);
+    }
+
+    // Stack leeren – clearStack muss alle StackNodes freigeben
+    clearStack(stack);
+    stack = NULL;  // Pointer selbst auf NULL setzen
+
+    // Auf leerem Stack dürfen die Operationen nicht crashen
+    assert(top(stack) == NULL);
+    stack = pop(stack);
+    assert(stack == NULL);
+
+    printf("...OK\n");
+}
+
+int main(void)
+{
+    printf("Running stack unit tests...\n\n");
+
+    test_push_pop_lifo();
+    test_empty_stack_operations();
+    test_clearStack();
+
+    printf("\nAll stack tests passed.\n");
+    return 0;
+}
\ No newline at end of file
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new file mode 100644
index 0000000..94a4f04
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diff --git a/test_stack.o b/test_stack.o
new file mode 100644
index 0000000..e089924
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diff --git a/timer.o b/timer.o
new file mode 100644
index 0000000..e9e8e8e
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