I like the style and design of this map. It was a great idea to do something like that. However, there are a number of issues that need to be resolved. I don't understand why there are invisible walls in these two places.
This room is completely empty, as if unfinished. When I first saw it, I thought it was a door that could be opened. However, it turned out that these are just brushes, behind which there is nothing. This room definitely needs to be finished.
Since there aren't many places to camp on the map, this means that there will often be many players at each camping spot at the same time. So this creates additional balance issues. This place can become impenetrable to zombies if there are 10+ players with machine guns.
So you need to add an additional entrance to this room from the back or side that will be covered by brush that can be broken fairly easily to open it.
The passage should be for a crouching player only, about 2 players wide. Then zombies will have a better chance to reach people. And accordingly, you will have to remove invisible walls in the aforementioned places, this will be for the better and will expand the playing area of the map.
Also, in the same place, but outside, you can make another point for camping. It is enough here to add 1 or even 2 ladders on the sides.
And there will be a camping place on the roof. Or you can even add a narrow and low roof pipe to the roof, like this one.
There is a lot of free space on the sides of this room.
It should be filled. You can also add camping spots, like this one.
You can make camping points out of these arches. To do this, it is enough to add a ladder so that you can climb up as I have drawn in red on the screenshot.
However, there are places where it is really worth installing invisible walls for balance. Since it will be possible to climb the ladder to the arch, it will be possible to run along the walls of the room this way.
Therefore, this will create an additional path for the zombies to put even more pressure on the camping points, which will make these points extremely difficult to defend, so it is necessary to install invisible walls in such a way that the players can only partially walk there, and then zombies will not be able to attack this way
In this case, invisible walls should be installed in these places.
Maybe my suggestions will spoil the style of the map a little, but they will give it more functionality.