The code was the one you send me, but i fixed the problem, it was simply an error with #define (I've written #Define x=2 as I added you part to my code, then I've seen my huge mistake).
Now, you said me I do not understand Serial communication, it's right, as I wrote Serial.flush() I was trying to clear the buffer, so that the data will be the newest possible. How does I clear the buffer?
Thank you for your help!