In the movie Hermann Löns' cousin Rosemarie fells in love with Löns. In real life it was Hermann who fell in love with his wife's younger cousin Hanna, which also happened in 1909, which later led to a divorce between Löns and his wife.
Unlike in the movie were Löns was called in to join the army in World War 1, in real Life Hermann Löns was a volunteer and joined the army by his own free will. He even tried to join the troops by connections.
Hermann Löns' wife Lisa remains with him until the end in the movie. In real life she left him in 1911 after she found out about his mistress and after Löns did a gun shot in his own home due to a nervous breakdown. Löns also didn't stay in Germany but traveled for a year through Europe.
The opening of the movie sets the first scenes in August 1906, since Löns' 40th birthday is mentioned. His wife Lisa Löns is seen walking around freely with no problems. This is very unlikely since she gave birth to her son Dettmer only two months before that. Dettmer is not mentioned or portrayed in the movie at all.
In the final scene, set during the start of World War 1, (in which Löns died shortly after it started) Hermann Löns is planning a future with Lisa. In real life he wasn't married at that time after his divorce with Lisa in 1911.
The first part of the story suppose to be set in 1906. However the printed poem that Lisa is holding is Hermann Löns' "Verbotene Liebe" (Forbidden Love), which was released in the poetry book "Der kleine Rosengarten" (The little Rosegarden)in 1911.