Here's Fassbinder's German classic Ali: Fears Eats the Soul which is a remake of the Douglas Sirk film All That Heaven Allows which I actually wrote about, so check that entry out as well.
Where the film mainly diverges is removing the class division of the original film (with a wealthy widow falling in lover with a gardener) and instead adds a racial aspect in addition to the age different by having a widowed office cleaner falling in love with an Arab mechanic.
The story begins with Emmi (Brigitte Mira) stopping into an Arab bar in order to avoid a rainstorm. There she meets Alie (El Hedi ben Salem) and the two begin a romance that threatens their social standing as the two deal with racial prejudices at the time.
The film is going to be hard for some people to watch. Since it's a very Brechtian film. For those who don't know, Brecht was a figure in German theater who believed that theater (or in this case film) should not cause emotional responses in the audience instead we should take everything at face value and reflect on it. In other words, theater should be all head (No pun intended) and no heart. Because of this, the dialogue can be presented in an almost monotone manner by some of the actors and some more emotional moments are hampered by the fact that the film is dubbed over. I don't mean that I'm watching an English dubbed version, but all of the German dialogue was dubbed over post production, so you have moments where audio doesn't 100% match with that's going on the screen so it can be jarring.
If you can get past this method of acting, you'll find a very well-balanced story. It's far too easy when dealing with stories about forbidden love to have the central relationship as this perfect entity that is threatened by societal forces. Well, this isn't true in the film. We get to see that the differences in age, race, and culture do make a difference and that maybe this isn't a perfect pairing.
The film is also a rich commentary on society and human nature, with a lot of focus on what it means to be an outsider, the circumstances surrounding it and the ways in which people are asked back into society and the reasons why.
It's not going to be loved by everyone, but it's a film that has a lot to say and does so with an interesting twist on the melodrama subgenre.
And if you are interested in watching it, I also suggest seeing Douglas Sirk's original film since there's references to the original within this retelling.