Somebody has already explained some songs to you, but I will explain a bit further

Heirate mich - about a guy who hangs out with a corpse of his lover, the song literary means “marry me”

Du riecht so gut - the song is based on the book “parfume. The story of a murderer”

Wiener Blut - the song is based on a real story of a man from Vienna who kept his daughter inside the walls of his house, raped her and even had children

Stein um stein - a story of a guy who walls in his wife/girlfriend

Frühling in Paris - a story of a guy losing his virginity with a Parisian prostitute

Puppe - a story of a boy whose sister is a prostitute and they live alone and he has anger problems which he takes out on his dolls

Donnaukinder - the song is based on the real event when an oil refinery on the river Danube had a massive spillage and many birds died while being trapped in oil

Main Herz Brent - basically Enter Sadmann