If you still don't have a machine gun this will be tough.
Get one as quickly as possible, then go for the Gold Key.

This level is the first where you come across my "Poet's Dead Guard Trick", getting you locked into a new area. If you enter the maze without having picked up the Gold Key, you have to find a secret passage back to the main hallway.

Clear the room in front of the elevator, get the Silver Key and move back through the short cut in the north-eastern part of the floor. But prepare for some more fighting.
Push the block with the sign and get to the elevator.