Weird patterns appears behind some menus and using Mission Control

I recently updated to macOS High Sierra 10.13.5 on my old mid2010 mbp. Soon after the update I began to notice weird pixel-like patterns appearing behind some menus. With time I noticed they appear especially in menus which are supposed to be translucent. I then noticed they appear during the animations when using Mission Control or App Exposé. I could live with it, but I later I found out that working with Parellels it's practically impossible.

I don't know if this is either a hardware or software issue.

Please help.

Or maybe it's time to throw this 8 y old mbp away.