- Players with the resupply box can climb on lamps, the rock, pipes, building edges and the helicopter (This blocks the takeoff animation). You have to cover these parts with "player clips".

- The zombies do not attack if you are standing in certain areas. For example the ramps and behind the desk. You have to use info_node and info_node_hint. You can check how they are connected in-game with "ai_nodes" and "ai_show_connect 1" .

- Zombies appear in front of the player at the site where the bomb is planted. Here you have to use "spawn_controlarea"

- The zombies do not attack if you are next to the helicopter. Info_node is missing here. I guess you didn't put them there so they don't spawn there. You can put info_nodes and a "spawn_controlarea" to prevent them from spawning but walking around.

- The yellow and red line does not really indicate where the escape area begins.

- The escape time is maybe a lot (this is just my opinion).

The guide made by the developers has the information I mentioned.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=493806250

It's a good map. I'm waiting for an update