Boxeur

Who also had an uncle who was a coach, was also a Polish champion, emigrated at a similar time and had a similar relationship with his wife. At the beginning of his emigration he also couldn't find a job and when he did fight they gave him weak opponents (supposedly). His private life was also similar to the film (he broke up with his wife and later got back together) and eventually he also returned to Poland. Apparently he didn't agree for the film to be his biography because he wouldn't have come out well in it, but it's hard to believe that the scriptwriters didn't communicate with him. I think this is the true story of boxing in Germany then and maybe now.