The book Lena (Josephine Preuß) reads at the beginning of the movie ("Wer bin ich und warum gerade ich") doesn't even exist.
Despite sharing much of the same cast and creative crew as Türkisch für Anfänger (2006), this film is not a sequel or set in the same continuity as the TV series. Rather it is an alternate telling of the story.
In the movie Cem (Elyas M'Barek) calls Lena "Gurke" (German: cucumber). This is a nickname for Lena (Josefine Preuss) used by her mom, Doris (Anna Stieblich) in the series of the same name.