A small nit-pick. Quadrophenia is set in 1965.
I have heard good things about Four in a Jeep , a political parable about the allied occupation of Germany.
Filmed on location in Germany just a few years after the war, I Was a Male War Bride features some very 8interesting period footage. Unfortunately, it also features some of the worst comedy writing I have ever heard delivered. Watch with the sound off.
A Foreign Affair seems to be well-liked on the IMDB
Another small nitpick: I have not seen Four in a Jeep myself, but by all accounts it is set in Vienna not Germany.
True, but the OP asks for films from 1946-1990. “Postwar,” I’m guessing, has come to mean “from the end of WWII to the end of Communism.”