Wie alt bist Du? means: how old are you?
Translated from the German, it means "where are you?".
Wo bist du means Where are you in English.
Du bist translates as you are.
That is incorrect grammer. You would actually say ich bin which means i am.
If you use bist you use it with du so it would be du bist which means you are
It means: Who are you?
Wo bist Du = where are you
Bist du das = Is that you
You are fast.
Bist du = are you (informal, singular)
Du bist der absolute Hammer! = You are totally awesome!
Du bist so weich = You are so soft
translated it means are you ready
It means "When will you be at home?"
bist du in Ordnung = are you okay
"Du bist bärenstark" means "You are strong like a bear" (literally) or "You are husky". But in colloquial speech the word "bärenstark" can also mean "really awesome". So it depends on the context.
Du bist eine hübsche Frau, du bist süß. = You're a pretty woman, you're sweet.
"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 nett = you're nice, or you're kind.
du bist scharf = you are sharp