Downloaded maps not working

I bought portal a while back and I recently downloaded garrys mod, and then team fortress 2. I have been downloading maps but have been having problems with some of them. Namely the more complicated ones like the suburbs map and evo city map.

The maps come out with the textures being replaced with pink and black checker board type coverings and some come out as just the word error.

only simple maps seem to work… and all the information on the maps just say “put in addons folder” or “put in maps folder” but nothing on how to fix problems

any one have any ideas?

go into gmod
click on gmod settings in the menu
and then check all the games you have
restart gmod

also
some maps come with extra materials you have to place in
or if its addon map
then you have to be careful
drag and drop the folder that has the info file in it

You own the games Portal, Team Fortress 2, and Gmod, but that is all, correct?

You are more than likely downloading maps that use Counter Strike materials, as most city-based ones do. Half-Life 2 textures and models come with Garry’s Mod, so that along with TF2 and Portal means that you should be able to download a bunch of maps, but read the descriptions carefully, and if it says it was made for TF2 or Portal then it will definitely work provided you checked the game off in your Garry’s Mod settings. If it says it needs CS:S, then do not download it, because it will not work.

DAMN! all the good ones are city ones :-\

the descriptions dont really say enough sometimes