All the German you need to know.
Ein Bier bitte and Wo ist die Toilette?
Actually on my first visits to the Harz the year after the wall came down I needed a lot more German than that. Nobody spoke any English, unlike West Germany where it seems like everybody speaks some English. Students in East Germany had to take Russian instead of English.
Now of course, English is spoken at any business that deals with tourism, which pretty much means everywhere in the Harz Mountain region. Still, learn a bit of German and people will appreciate your effort.
Michael Allen