For a while a know how to make weapon skins with a program slab6. But after i replased default skins with my weapon skins, i can't run the game - client.exe write to me: invalid game file. What i should to do, to play aos with my skins and without errors??? :-(

first they must be name semi.kv6! Secound of all before you mod... (and i hope you did this) always make back up files in case things like this happen! :)
P.S the gun name must be semi.kv6

Certain parts of re-skinning, whether weapon or player, can have restrictions upon sizing.
Most 'Invalid Game File' errors are caused by over-sized (or wrongly sized) reskins.