The solution to your problem is:
#include <stdio.h>
char* func(char* array, int length, int position){
char* out = (char*)malloc(length*sizeof(char));
int i;
for(i=0;i<length;i++)
{
out[i] = array[i+position];
}
return out;
}
int main(){
char array[100] = "Hello, my name is Ivan.";
char* out = func(array,5,18);
printf("%s\n",out);
}