It often looks like the crew on the conning tower deck is one step up in comparison to the crew in the wintergarten, but there were some "steps" inside the 'conning breast wall' to climb a little up and have a better look (even onto the hull and deck).
This is only a model, but it shows the conning tower deck to be at one level - without a step down - to the wintergarten. Look at the guys inside the breast wall - i.e. the red bearded sailor and the Kaleun - they are at one level with the crew in the wintergarten.
http://www.ipmsdeutschland.de/Marine...558_Krech.html