Hello, my problem is that when i move the screen in the game ( In a mission ), in some places the screen change to very bad quality ( Big lines where the game is smearing )

I dont know what is my screen size but im using on windows size 1280x1024 i like this size ( Windows prefer 1680x1050 but i dont like it ), in the game im using screen size 1024x768 (4x3), now what i can do to fix this bug?

Ps. my deskopt is wery big like 2x my head, im 16