Actually I understand like 30% of that songI used to learn deutch (I`m from Poland by the way), but now I`ve forgot most of it. Nevermind, I get the umm... general point. And a little more after googling lyrics cos reading is always easier.And as far as Snapes character goes you can`t forget that Dumbledore believed in people changing and really needed someone to protect his young warrior aka Harry during his time at Hogwarts. On one side it maybe was traumatic to some children but on the other hand potions are kinda dangerous so that kind of teacher might work better than expected (pupils need to be careful etc etc).