need help with mw2 :=|

i get like 4 kills, then someone kills me from behind. am i running to out in the open to kill them? And sometimes they blend in with the wall. What can i do to not die as much?

Practise. A lot.

Haven't we had like 15 threads like this in the past week?

Yes. Its getting irritating at this point. Nobody is going to help you win the game. Stop sucking, man up, and practice. Nobody is good their first time.