Neatly observed and deeply felt on a scene by scene basis, it all seems just a little bit too blunt and a little bit too broad overall. The racism on show is somewhat cartoonish, making the (potentially interesting) thawing of some of the attitudes in the second half less believable, unbalancing the film as a whole.
In fact, the whole idea of self-interest and pragmatism overcoming bigoted beliefs (as depicted by the shopowner), and whether this is the first step towards a more tolerant society, is touched upon but never really developed, leaving the relatively simple relationship drama, which is not terrible by any means, but hardly awash in original insight.
Fassbinder does have a knack for framing to emphasize the isolation felt by the central couple (doorways, a sea of benches etc), and the wearing down of Ali’s genial optimism in the face of such overwhelming hostility is affecting, especially given his otherwise rigid posture. Even water will wear away rock given enough time.