meantime I just wanted to know in short 'how to add an integer to a char array
That depends on what you mean by adding an int to an array.
Do you want to convert the int to a string, and then append that string to an existing string? If so, there are several ways. You could use itoa() to convert the int to a string, and then use strcat() to append it to another string.
Or, you could use the sprintf() function to that in one step - you know the function I mentioned in the first reply.