During the late 1920s and early 1930s zeppelins made regular trips across the Atlantic between Germany and America. For a short time they were the fastest means of trans-Atlantic travel.
Johann Trollmann was a real person. Hannes Wegener also portrayed him in the documentary Gibsy - Rukeli Trollmanns Kampf ums Leben (2013).
Songwriter and bandleader Max Raabe appears briefly a singer Emil Engels in the dancing scene. He wrote the song "Ein Tag wie Gold" which has been used throughout the fourth series.
Gereon and Charlotte bet 3 marks 90 pennies on Trollman to win. The odds are 5 to 1 against Trollman so when he wins Gereon and Charlotte would collect their original bet of 3.90, plus 3.90 x 5 = 19.50. So they win 3.90 + 19.50 = 23.40.