Why don't I have a custom title by now!?
Well, I've done it. And my feelings are mostly very positive. For a first map, it's pretty good, both aesthetically and gameplay-wise. I liked that the map wasn't entirely linear. Nonlinear maps are good, don't be afraid to add on that aspect. Map was quite spacious and corridors not cramped, which is good too. I also liked the weapon distribution throughout the map (powerful weapons given soon), the attempts to make use of height variation, the fact that I immediately saw what every switch did, and overally the easy-ish pleasurable gameplay (yes it is). Music is nice too.
I noticed a few basic mistakes you'd better try to avoid in the future. First, the map is quite very orthogonal. Not that it's a big flaw, but since the Doom engine allows for angled walls, it's better to take advantage of it as much as possible. Second thing, typical for newcomers, is monotexturing. You have rooms entirely covered with white STARTAN texture, or silver SUPPORT2, or a gray texture, computer panel etc., and it's really just this texture covering the square/octagonal room all over, like a wallpaper. The best is to already design the rooms to allow for meaningful texture changes and detail. Add alcoves with monsters, more windows to surrounding areas, merge/interconnect rooms with each other. Interesting architecture adds a lot to the map's quality.
Another thing, this time a more important mistake, is the inescapable nukage pit. Inescapable pits are generally considered an annoying design choice, never make them, always provide some way out. Then I personally didn't like how some of your doors can't be opened from one side, I don't really see the reason. When you do it, at least use a D1 action so the door stay open, plus possibly give the door a different colour, so it's distinguished from normally openable doors. Lastly, the map kinda lose an action towards the end. The thing I'd recommend here (an actually good thing) is to add some monster closets that open somewhere in the map in the moment the player grabs a key. Then, when he'll backtrack to the coloured door, he will suddenly face a new opposition.
Wish you good luck with your further mapping!