Gmod textures missing

Hi i have just bought Gmod and Counter strike source on Steam and i went into a prop hunt game and all i could see was purple and black everywhere and error signs can someone help me out here i don’t know what i need to do to fix this thanks

Make sure you mounted CS:S by checking the option in the mount menu (bottom right of main menu, game controller).

I just checked and yes the box in the bottom right corner for css is ticked what else can i try

What map is this happening on?

It is happening on all maps for me. My controller (on the bottom right part of the screen) has a bunch of x’s on a lot of the names and has files with a minus sign. Just bought the game last night and haven’t done anything to make this happen.

Have you installed and started up CS:S?