GMod Map Problem

When I join any map besides Flatgrass it is always looks dark and it gets SUPER laggy. Like downtown RP’s I join them and all the buildings are black and have wierd designs on them. Same with contruct like this.
Wierd Designs:
And when I walk up to it and shine my flashlight, then it shows the buildings texture like this:
Is it a problem with shaders? And when I open Gmod, right before it goes to the menu I see this:
Any help leading or fixing this is SUPER appreciated. I basically can’t play any servers when it’s like this. Oh, here is my computer:

I got this when I installed freespace revolution. I deleted it and reinstalled and it fixed it.

The thing is, I don’t have Revolution and it does this for EVERY map besides Flatgrass, which is starting to get boring.

EDIT: Fixed! Lowered my dxlevel to 80