I'd like to start by saying I'm not going to rate this because it is a first map, because I don't want you to either get too cocky if it's a good rating or get driven away because it'd a bad rating.
The pros: It's an exceptionally fun map and the shape of the map ( The different levels ) is very nice. You actually included lighting in your first map - most people don't do that. :( Well at least I think you did - It's kind of hard to tell with light_environments.
The map is very repetitive, for covers you only used blocks, the map is nearly symmetrical. Worst of all you only used two textures, you should try to refrain from doing that, it makes the map look much worse than it could.
The Improvements: As I said, use a variety of textures and covers. Also try to leave the options open for people by kind of having separate sections, which I guess you kind of did but both sides can see eachother.
Make sure you always cover spawn points with a wall or something or there will be loads of yucky spawn killing. :(
Overall it's pretty nice for a first map but do some more experimenting with different ways of lighting, other cool covers, props etc. before releasing a new map. Also try to spend some more time on details.