This map is playable but unfinished. Due to the important message at the end "I hate this map" by the mapper my guess is that the mapper hated this map and left it as is.
So far I see only one thing broken, and that is the two GMans hiding in a corner, who activate their scripted sequences (which are the same) just as you finish the map.
My guess is that there should be only one GMan, doing the sequence at the beginning of the map, since you are not supposed to see a gman hiding in a dark corner which makes no sense. This also triggers some enemies teleporting.