It means "Short question, are you in Berlin?"
Bist du = are you (informal, singular)
Wie alt bist Du? means: how old are you?
Du bist nett = you're nice, or you're kind.
You are audi
You are fast.
Du bist der absolute Hammer! = You are totally awesome!
Du bist so weich = You are so soft
You're a gem
In English: "You're an idiot."In Deutsch: "Du bist ein Idiot."Or "Du bist ein Dummkopf".Please note proper spelling of "you're" in the English.
"Are you with me?" That would be a translation of the question "Bist du bei mir?". The start of the sentence as in the Bach/Stölzel aria "Bist du bei mir, geh' ich mit Freuden" would be better translated as "If you are with me (or: if you're near to me), I go light-hearted (or: with gladness)".
Du bist schön.
It means "When will you be at home?"