The Goliath Pionier was built as a convertible, as a notchback sedan (the most common version) and from 1933 on also as a fastback sedan. There were two different versions of the fastback sedan: an earlier one with rectangular doors and side windows cf. attached picture), and a later one (as in the puzzle picture) with slanted doors and windows and a more flowing roofline. I even found a picture of the later one with integrated dickey seat.
