An important note to start off: there is no a German version of Kafka’s book Der Prozess. The German film of this title, released in 1948, has a WWII focus. This production was done in English, directed by Olson Welles, and combining French, Italian, and German efforts.
Romy Schneider may be our most famous German-speaking cast member. She plays Leni here, but the world remembers her for her role as Sissi five years earlier.
Max Buchsbaum, who plays a magistrate, is a German actor who seems to have mostly worked on German language projects beginning in 1960.
Max Haufler, playing Uncle Max, was a very famous Swiss actor – the first to transition into Hollywood. He was successful through the 1950s and 1960s, but hung himself, supposedly due to failures in his personal life, in 1965.
Wolfgang Reichmann plays a guard. More information about his films and his focus on films from important literature can be found in the post on Woyzeck.
The final German speaking actor in this version is Thomas Holtzmann, who plays a law student. Like Reichmann, he appears in many films relating back to literature, such as König Ödipus, Michael Kohlhass, and Dantons Tod.
The German version of this film is not well dubbed. In fact, there are scenes, both partial and full, that have the original English voices. Those sections are subtitled in German.