So, I just downloaded and explored this map, and looks very promising and interesting, especially since there isn't a single map where the fight is entirely focused in closed spaces.

However, I found a lot of issues of various nature, and I'm going to list and explain them:

First things first, the division of the teams areas. There is no fast way to distinguish RED from BLU, unless closely looking at every detail or remembering the layout.
Everything is built with a reddish wood, which is a material mostly used for RED areas. BLU is usually distinguished in any official/approved map by making the BLU areas in concrete and industrial looking, while RED wood and rustic looking. It is part of the official teams' design.

Another fatal design flaw is the deadly pit. Unless you fall for it, there is no clear way of understanding it is an ambiental threat.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810024628
If you look at it, it's so close to the map level that you might as well thing it may be explorable.
An easy fix is to make the pit look like a real pit. Make it VERY deep, don't put elements of interest like doorways (if you follow one of the map commentaries, the Valve map designers specifically say in one part that they avoided any possible element of interest outside the map) and make the slope steep.

Another design issue is the lack of proper boundaries for the point cap area.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810024277
In a lot of spots players are unable to cap, despite they may think they are doing it.
A fix is to either rework the shape and size to match the cap area, or to draw on it the perfect boundaries, like some official/approved maps do.

Still talking about the point, this giant log has no sense to exist:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810026457
The other side doesn't have it and looks totally fine.

Another main issue to be reworked are the spots where the floor goes wild and you can get stuck to the wall details, like here:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810025921
Or even here, which also has an additional weird and surely unintentional look:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810025042
Not only it is easy to get stuck, but also many of those areas are too claustrophobic; players have little space to move around, the walls are in the way, and both who is attacking an enemy or defending himself finds out how those paths are a death sentence for splash damage weapons. Making the terrain decent and smoother, and enlarging a bit those tunnels may help and feel better.
Staying in theme, this:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810026172
has totally no sense to exist.

Another issue is the lighting in some areas, like spawn exits.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810025193
There is no logical way to tell where the light comes from, and also it doesn't look very nice. It could have some rebalance, and if you like to mantain it something close to white, make a logical visible source like an electric mining torch.
You should also please note that there is a light bleeding issue in that same image and also in many other areas of the map, like here:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810025365
I am not sure about the origin, it may be caused by the external lighting.

Finally, a minor issue that can be easily solved:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=810023922
Clipping issue with a barrel.

I hope this may be of help to greatly improve this map and make it a lot more enjoyable.