As an east Berliner we have trams and no double deckers, but I have only seen double deckers near the center of the city.
I can't remember seeing them in the places with trams, but I don't see them much at all. This is my limited observation, as I don't use busses as much as trains and don't know the west as well as the east.

If you really care I can cycle out (in?) on the weekend and check.

Edit: added my bias