diff --git a/bintree.c b/bintree.c
index 5cf82a9..6a95f4e 100644
--- a/bintree.c
+++ b/bintree.c
@@ -10,10 +10,43 @@
 
 // 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)
-{
 
+// Hilfsfunktion: neuen Knoten erstellen und Daten kopieren
+TreeNode* newNode(const void* data, size_t dataSize) {
+    TreeNode* node = malloc(sizeof(TreeNode));
+    if (!node) return NULL;
+
+    node->data = malloc(dataSize);
+    if (!node->data) {
+        free(node);
+        return NULL;
+    }
+    memcpy(node->data, data, dataSize); // Daten kopieren
+    node->left = node->right = NULL;
+    return node;
 }
+TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize,
+                    CompareFctType compareFct, int *isDuplicate)
+{
+    if (root == NULL) {
+        *isDuplicate = 0; // kein Duplikat, neuer Knoten
+        return newNode(data, dataSize); // neuer Knoten wird Wurzel
+    }
+
+    int result = compareFct(data, root->data);
+
+    if (result < 0) {
+        root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
+    } else if (result > 0) {
+        root->right = addToTree(root->right, data, dataSize, compareFct, isDuplicate);
+    } else {
+        // result == 0 → Duplikat
+        *isDuplicate = 1;
+    }
+
+    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,