Why oh why does everybody recommend this sh*itty Borchardt? You only get decent service there, if you are a celebrity. Don't go there. And it is not even close to Bismarckstrasse.
Go to Restaurant "Florian" in Grolmanstrasse oder "Essen Fassen" in Knesebeckstrasse or "Nussbaumerin" in Leibnizstrasse. I know them, it's my neighborhood. The best gutbürgerliche Küche you can get here.