Good Evening Boa noite Boa noite – note that the same word, noite, is used for both evening and night.  Switch from saying ‘boa tarde’ to ‘boa noite’ around sunset.
 
Good Night Boa noite Boa noite
 
Note:  You can mix Olá with bom dia, boa tarde, boa noite to make another fairly informal greeting (eg. Olá, bom dia)
 
Goodbye Adeus Adayush – lit. “To God”.  Note that you can use bom dia, boa tarde, and boa noite to say goodbye as well.
 
‘Seeya’ Tchau Chow – this is a Brazilian expression, but is widely used by Portuguese as well.
 
See you later (same day) Até logo Atay logu – lit. “until straight away”, which doesn’t really make sense, but then neither do a lot of things in Portuguese!
 
See you later (another day) Até amanh? Atay aman[ng]yah – lit. “until tomorrow” – used even if you won’t actually see the person for a few days.