Hi! As the others said, "buona notte" means "good night". But, considering that english is not your native language, perhaps it´s important to advert you that GOOD NIGHT means that you are leaving the place at night, that you are actually saying bye bye to people at night (going home to sleep)! In English, if you want to say "Hi" at night, just say "GOOD EVENING". The correct translation of "good evening" to italian is "BUONA SERA", not "buona notte". If you wanna say "how are you doing" in italian, just say "COME STAI? (TU - INFORMALE)" or "COME STA" (LEI - FORMALE).