hello, I recently bought Doom 2 on my Mac. (Os Catalina). It doenst work. It says that it should? maybe I dont know something?

DOOM II is a windows game, it's not compatible with Mac OS. If you accidentally purchased it I would recommend that you contact GOG Support and see if they will refund you.

If you do want to play it on your mac, it is possible but quite complicated. You'd first need to extract the WAD file from the windows exe, either by installing the exe using Wineskin, or by using Innoextract, then you'd need to use a Source Port (such as GZDoom) to play the WAD.

The version that is sold on the store is using the windows version of DOSBox.
DOSBox is available for all systems and can be downloaded from here.

Alternatively you can check for source ports like (G)ZDoom that also work with Mac.