diff --git a/numbers.c b/numbers.c
index 61ddf4d..8b7c0b5 100644
--- a/numbers.c
+++ b/numbers.c
@@ -31,9 +31,7 @@ void createchecknumber(unsigned int len, unsigned int numbers[])
 
     do
     {
-      unsigned int value = 0;
-      value = (rand() % (len * 2) + 1);
-
+      unsigned int value = (rand() % (len * 2) + 1);
       same = 0;
 
       for (unsigned int j = 0; j < i; j++)
@@ -56,6 +54,11 @@ void createchecknumber(unsigned int len, unsigned int numbers[])
 
 unsigned int *createNumbers(unsigned int len)
 {
+  if (len < 2) //sonst Index-Auswahl-Dauerschleife
+  {
+    return NULL;
+  }
+
   if (RANDOM_SEED == 0)
   {
     srand(time(NULL));
@@ -68,7 +71,7 @@ unsigned int *createNumbers(unsigned int len)
   unsigned int *numbers = malloc(sizeof(unsigned int) * len);
   if (numbers == NULL)
   {
-    return 0;
+    return NULL; //
   }
 
   createchecknumber(len, numbers);
@@ -78,9 +81,6 @@ unsigned int *createNumbers(unsigned int len)
 
   do
   {
-    i = 0;
-    j = 0;
-
     i = rand() % len;
     j = rand() % len;
 
@@ -89,7 +89,6 @@ unsigned int *createNumbers(unsigned int len)
   numbers[i] = numbers[j];
 
   return numbers;
-
 }
 
 void sortnumbers(unsigned int numbers[], unsigned int len)
@@ -109,15 +108,20 @@ void sortnumbers(unsigned int numbers[], unsigned int len)
   }
 }
 
-// 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) // sonst Index-Auswahl-Dauerschleife
+  {
+    return 0;
+  }
+
   unsigned int *copynumbers = malloc(sizeof(unsigned int) * len);
   if (copynumbers == NULL)
   {
     return 0;
   }
-
+  
   for (unsigned int i = 0; i < len; i++)
   {
     copynumbers[i] = numbers[i];
@@ -127,15 +131,15 @@ unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
 
   for (unsigned i = 0; i < len - 1; i++)
   {
-    if (copynumbers[i] == copynumbers[i+1])
+    if (copynumbers[i] == copynumbers[i + 1])
     {
       unsigned int a = copynumbers[i];
-      free (copynumbers);
+      free(copynumbers);
       return a;
     }
   }
 
-  free (copynumbers);
+  free(copynumbers);
 
   return 0;
 }