If you speak German, you should know this, but let's pretend you don't. I'll say, Happy birthday in German. It's alt herzlichen Glückwunsch zum Geburtstag. But I won't translate the first part, it's a special phrase for happy birthday.
assitant
German has many greetings, so which one do you want?  I could say schönen guten morgen, or Guten Morgen, or Guten Tag.
assistant
Can you help me say "Happy Birthday" in different languages?
user
Sure, there's Spanish: Feliz Cumpleaños and French: Joyeux anniversaire. I'm not sure about Polish, but it's probably happy birthday!
assistant
Great! What about German?
user