There are many options.
Usually you can learn or read, that "goodbye" is "auf Wiedersehen", but as you are in Germany it is possible, that most of time you will hear "tschüss" oder "ciao".
Same thing is with good morning/good afternoon (guten Morgen / guten Tag). When you go shopping fast all of the Cashiers will greet you with simple "hallo" or "moin"
