Something went horribly wrong

ok so i open up garry’s mod to play and i start up Dm_overpass (singleplayer) and all the textures look wrong and my props are showing up black, plus no lighting effects work, so i try again and start up Dm_Steamlab (singleplayer) and same problems, here is what it looked like:

See? if anyone could help that would be great

Fullbright is turned on, I believe the command to turn it off is Mat_Fullbright 0

Also, for a further tip. This occures when you have previously loaded a fullbright map, so a gmod restart will also work.

oh ok thanks