Alright so I ran around your map for a bit and this is what I have to say:
Why is there water here? There is no point for it in a gameplay sense. Also, use a tf2 water texture
There's a lot of these nonsolid lamposts that look like you can jump on them around the map, make them solid, clip them off, or remove a few of them
use shutter doors in gameplay spaces, it doesn't really help block a sightline because a sniper can play peek-a-boo to the enemy spawn
Shutter doors are pretty bad but team-specific shutters in gameplay spaces are really annoying to fight around, what's even the point of this door? There's another health pack nearby
You can type mat_leafvis 3 in console with sv_cheats 1 on to view the visleaves that are rendering for players in real-time. It looks like you put your map in a giant skybox cube, which means that a lot of stuff that I can't see is rendering anyway. Look around in the decompiled valve maps and see how they do skyboxes
Missing noentry sign here
What's the point of this cover when I have to cross a sniper sightline to get here? I don't really see the purpose in this balcony, snipers look like they'd be pretty good on this map without it.
Snipers can peek only their heads over these boxes, which is pretty cheap as the sniper is hard to see/attack
Put patches under all hp and ammo drops, it may seem trivial but people need to know where this stuff spawns
There isn't really a point to this 2nd story, maybe add an exit up here?
Also worth noting is that you can click this blue button here so you don't have to create a new map thread every time you create a new version of your map. Make sure you change the map string name!