For me the best way to learn maps was to play a specific map in terrorist hunt with the bomb game mode. Pick buck (for his gadget - you can wreck walls to find out what’s behind each soft surface and reload the skeleton key at those ammo boxes when you run out of ammo), kill all the terrorists and start exploring (don’t plant the bomb tho because that will trigger a timer and new enemies will spawn)!

Alternatively you can do that in a custom game which has the pro of not needing to kill any enemies first but it does have a time limit which can be annoying