Issue persists:
1. If using a config, remove it and only run commands such as r_3dsky and r_shadows
2. Unsubscribe from all addons on Steam workshop, go to your garrysmod file directory run the .bat file called "Factory Reset Garry's Mod" after that (note this will delete everything, possibly your settings too)
3. In-case you have a bad PC, to avoid any issues with broken vehicles, lower the graphics settings except for the texture details. It is important to keep the texture details high