Hello!
The phrases for saying "Hi" and "How are you?" differs in
Brazil and Portugal.
Hi. How are you? - Oi. Como vai? / Oi. Como está?
That one is the most common in Brazil, but if you would
go to Portugal, the most common, if you are being
polite to someone that you don't know, is this one:
Hi. How are you? - Bom dia. Como está?
But if you the person already, then just say like this:
Hi. How are you? - Olá. Como estás?
I hope that this has been helpful.
Take care!
/Saïd.