Very bad Map glitch and lag

So any time I want to download a map from garrysmod.org and try t play it’s just completely broken, theirs errors everywhere pink and black patterns , and I know it’s not the maps because my friend downloaded the same map I downloaded and it works perfectly.
And before when I first downloaded garrys mod (for the first time obviously) most maps worked fine, but now ever map is glitchey and broken.

Big red ERRORS and pink/black patterns usually indicate missing files/textures/models. Those maps might use some objects you do not own (for example because you do not own EP1, EP2 etc.), and therefore they are displaying those faults.

If you own all the games you need to own for the map, your Gmod is probably messed up.

Regards

Person above is correct. A lot of maps also need CS:S textures. And before you ask, no, there is no way to get the missing materials without actually owning the games.

Ah, that must be why my friend can run many maps I can’t he has CS:S

Well thank you for informing me because i thought it was my video card.