Can anyone help me find sheet music for the song 'Warum'?

Hello, I am 17 and have been studying classical music under a private teacher. I came across a video on YouTube of a particular song that I began to favour called Warum by Theo Mackeben. I've been searching on all sorts of search engines for the song and I cannot find the sheet music for it. I would like to have it as a possible piece to sing for district contests or for music scholarships. Can anyone help me find the song? It would be greatly appreciated if anyone could find a possible link for the sheet music.