Traudl Junge, Adolf Hitler's "last" secretary, was interviewed by Michael Mussmano several times; part of her recollections were included in his "Ten Days to Die" from which this film is adapted. In Junge's memoirs, "Until The Final Hour," she says that Mussmano helped arrange for her to spend two weeks in Austria advising the director during filming, for which she was paid DM1500.
When Bruno Ganz was offered the part of Adolf Hitler in Downfall (2004), he had serious reservations; what changed his mind was Albin Skoda's performance in this film.