Ah, yes, I love apfelwein, too. I have had it (and like it) both finished/aged and also really young (like Federweisser or Neuer Wein) in the fall. I think for me it is as much about the experience of getting it in an outdoor market (like the one you pictured) as it was about the product itself. However, I do recall I had a lunch at a sit-down place in Frankfurt, and I couldn't tell you anything at all about the meal, but I still remember how delicious the aged apfelwein was.
No, I cannot tell what's going on with that bellows. My best guess is that it was an "early All-in-One wine pump," and they are racking the wine off the lees from one barrel to another, maybe??