I loaded up the map on an empty server and ran around for some time, and this is the feedback I got. Remember, I'm trying to help you improve your map and not want to make it down.
Here are my thoughts:
First off all the map feels sometimes a little bit like a labyrinth. There are so many rooms and routes in your map that make it very hard to orientate. You forgot to add arrows leading the player to the points which make it even more complex to understand. I would suggest you go through each route after another and ask yourself: "What is the purpose of this route? Do I need it?"
This area for example isn't needed in my opinion. You almost need to go behind blu spawn and it doens't lead anywhere:
When you exit blu spawn arrows could really help to navigate. When I left the spawn I was unsure where to go because of all those possible routes:
For blu spawn itself: I feel like this area is misleading. I thought there was an exit, but it was just a window:
Why would I ever take this exit? The defenders have the highground and I have nowwhere to go after I left spawn:
You could try removing this exit and instead use the area I pointed out above as a new one.
Clipping:
The next important thing is the clipping on your map. It seems like you used blockbullet to block areas of, as I couldn't find any clip-brushes. The problem with blockbullets is, that, as the name says, it blocks bullets. This causes problems like this:
(The area behind this fence also feels like it is accesible, make sure it looks blocked of)
You can esaily fix this by replacing all blockbullet extures with clipping textures.
Also, why are there trigger brushes on the top of the roofs? I couldn't find out what they were doing.
Water:
Next thing: Why does this water hurt you. It's not enough to kill you, but it is annoying:
It also fells inconsistent that this body of water doesn't deals any damage:
I would remove the damage effect all together. It's never fun to get punished by the enviroment.
Trains:
You can get stuck when you ride the last wagon of the train:
The trainbell ringing non-stop is also very annoying. Why does it ring if the train comes by all 10 seconds? The sound is normally used to indicate, that a train is coming but by letting the train arrive so often the purpose of the sound is kind of missed. Just remove the sound or make it less loud at least.
Optimisation:
Please optimize your map. I didn't had any framedrops, but when you enter the detailing phase you should already optimze your map so far that only one big arera is rendered at a time. This is not the case for you map:
Sniper-Sightlines:
I couldn't find any major sighlines, but these are the ones I encountered. Playtesting will tell if they're a problem:
The only one I think is worrying is the one at spawn, as the sniper can see all three exits.
Random other stuff:
A ramp that is missing the front part:
Missing texture:
Drop-dpwn, that causes fall damage:
Brushes z-fighting:
I fell like this saw is not needed. It could be missed, when walking out of the water which causes a random death for the player which isn't fun at all:
Weird looking stairs, which look like you would fall through:
This concludes my thoughts on your map.
I hope these suggestions help you in your development.