I took just a quick look at your map and I found these errors (see pictures below). But the map generally looks good, especially lights.
I can't rate gameplay, because I didn't try that much, but I guess it will be ok. And I agree that the map is too dark. But the only what
it needs is choose different (brighter) ambient color I suppose.

Texture error. Probably will be needed even change scale.

Wrong rotation of texture.

Wrong position of texture.

Another errors in texturing.




It doesn't look good. Bricks should be visible at the front wall.

Very visible error in texturing --> unnatural look.

Same as probably all flags are placed in the air instead of being on the surface. Is there any purpose?
Hovering weapons are ok, but not flags I think. It should has fixed position.


These windows are too visible, that it is like there wouldn't be any.
I would use alpha material with high transparency more likely.
There is few more small errors, but mostly they are not so visible, because there is too dark.
Anyway, what I like the most on this map is interesting atmosphere and the shiny green water.
And with these corrections it will be even better in my opinion.