Dancing by the Wannsee

Whose photograph? I don't know, only that it was published in the Berliner Morgenpost in the good Weimar year of 1928.

The scene could well be a still of the film Menschen am Sonntag, from 1930. More about that film (in which a young Billy Wilder was involved), here:

http://www.weimarberlin.com/2019/01/menschen-am-sonntag.html