Bentley has put the poem into English rhyming verses, not an easy task.
"Bentley on Biermann- Songs and Poems of Wolf Biermann," Folkways Records, 2004 cd, originally recorded 1968. Camsco or Amazon can get it.

Some mudcat may have the recording and can help verify your transcription. An interesting poem, new to me.
My sole comment- since it is a German song, I would leave the elder brother as Franz (Harking back to the medieval poet Francois Villon).
In order to make the rhymes in English, Bentley departed from the German in some respects, so it is difficult to arrive at his lyrics from the German original, although, based on my poor German, he preserved the meaning very well.