Drehbuch translates to "screenplay" or "script". It's an interesting word because it's not commonly found in everyday song lyrics, making it stand out.
In the context of the song, the singer is heartbroken and wishes for a different outcome to his love story. He sings, "Yeah, ich will ein anderes Ende für's Drehbuch" (Yeah, I want a different ending for the screenplay), using the metaphor of a script to express his desire to rewrite his romantic fate and find a happy ending.
Have you ever been so heartbroken that you just can't stop thinking about someone? That's exactly what SDP is singing about in "Wie Viele Lieder Muss Ich Noch Schreiben?" [How Many Songs Do I Still Have to Write?]. This song is a super relatable look at trying everything to get over an ex, but nothing seems to work.
The singer is really struggling, saying things like "Ich kann nicht mehr schlafen, ich kann nichts mehr essen" [I can't sleep anymore, I can't eat anything anymore]. He's even resorted to Googling "Wie hört man auf zu weinen?" [How do you stop crying?], which, let's be honest, we've probably all done at some point! He's tried blocking his ex, redecorating his apartment, and even dating other people, but he just can't get her out of his head. It's a really honest and a little bit funny take on the messy reality of a breakup.