We need dxdiag and files from this folder to solve your problem. C:\Users\<Name>\AppData\Local\Arma 3 Alpha\

Can you upload it somewhere in winrar package please?
If package is smaller than 5,000k, so you can attach it here. Thank you.

(In case of random crashes, please install latest graphic and sound drivers. Usage of driver cleaner before installing new drivers will make sure you have no corrupted drivers left on your computer.)

i got PC FREEZ (screen freez) after sometimes 30 minutes, sometimes 5 secondes (after i join again the same multiplayer coop game)

here my RPT {F34405}files, and there is no other log files in my arma3 directory and here is my DX diag file