diff --git a/bintree.c b/bintree.c
index 5cf82a9..7e3eab7 100644
--- a/bintree.c
+++ b/bintree.c
@@ -12,7 +12,53 @@
 // 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)
 {
+    if(data!= NULL && dataSize > 0)
+      {
+        if(root == NULL)      //Abbruchbedingung: Keine Wurzel vorhanden, deshalb fügen wir hier einen neuen Knote ein
+          {
+          TreeNode *newNode = (TreeNode *)malloc(sizeof(TreeNode));
+          if(newNode == NULL)
+            {
+            return NULL;
+            }
+          newNode->data = malloc(dataSize);
+          if(newNode->data == NULL)
+            {
+            free(newNode);
+            return NULL;
+            }
+          memcpy(newNode->data, data, dataSize);
+          newNode->left = NULL;
+          newNode->right = NULL;
 
+          if(isDuplicate!= NULL)
+            {
+              *isDuplicate = 0;
+            }
+
+          return newNode;
+          }
+        int cmp = compareFct(root->data, 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
+          {
+            if (isDuplicate) {
+              *isDuplicate = 1;
+            }
+            else {
+              // isDuplicate == NULL → trotzdem ein Duplikat einfügen (z.B. rechts)
+              root->right = addToTree(root->right, data, dataSize, compareFct, NULL);
+            }
+          }
+          return root;
+      }
+    return NULL;
 }
 
 // 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.
@@ -26,9 +72,21 @@ void *nextTreeData(TreeNode *root)
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root)
 {
+    if (root == NULL)
+        return;
 
+    // Erst linken Knoten löschen
+    clearTree(root->left);
+
+    // Dann rechten Knoten löschen
+    clearTree(root->right);
+
+    // Dann eigenen Speicher freigeben
+    free(root->data);
+    free(root);
 }
 
+
 // Returns the number of entries in the tree given by root.
 unsigned int treeSize(const TreeNode *root)
 {