Jürgen Blin, who portrays one of the boxing coaches, was himself a professional boxer who won the European heavyweight title in 1972. He is best known for fighting Muhammad Ali on 26 December 1971; a fight in which he was knocked out in the seventh round after a fierce battle.
The final fight scene was shot as a long take that lasts more than 7 minutes and, according to the director, doesn't contain any hidden cuts.
The character of Tanne, played by Tobias Moretti, is loosely based on Hanne Kleine who was the founder and owner of the nightclub "Zur Ritze".
Shot in parts at the legendary nightclub "Zur Ritze", which is situated in Hamburg's red light district Reeperbahn. In the basement of the club there is a boxing gym still used for practice and local boxing events.
The shooting of the final fight scene has taken place at a venue called "Große Freiheit 36", which is known for its 58 gigs of the The Beatles in 1960 during their Hamburg years.