Need map help

every custom map ive downloaded is really screwed up. a bunch of items are missing, and replaced with big red ERROR signs, some surfaces are a bright pink and black checkerboard, and the sky is a copy of the ground. what can i do to fix this?

Do you have hl2 episode 2?

nope, just CSS, and DoD

There you go. Buy that.

[editline]10:50AM[/editline]

I’m sure it says you need Ep.2 in the map’s readme.