How do I infiltrate the Kugelstadt weapons factory on Bombed Factory part..

You have to get into the warehouse on the other side of the train. Kill the 2 on the catwalk and the 1 on the ground floor, then on the left open the double metal doors. There are 3 or 4 more that you have to deal with and then the metal door ahead of where you came in is where you need to go. Open it and get rid of the guy inside and go in and push the buttons on the wall. Go out the way you came in and the double doors to the left will now open. There are 4 guys on the first floor, and 2 on the catwalks and when they're gone go up the stairs on the left. Kill the guy in the office on the left near the top of the steps and when you get onto the walkway follow all the way to the other end of the room. Open the cover on the wall and push the button inside to restore power to the elevator. Go down the steps and at the bottom straight ahead at the end of the room the elevator is waiting. I can't remember if you have to push a button or if the level ends on it's own.