"Olá" means hello and "Adeus" means goodbye.  Portuguese speakers use "olá" and "adeus" a lot, so you can just use those instead of trying to remember any special phrases.
assitant
Oi and Adeus.
assistant
I'm visiting Portugal. Can you teach me some common phrases in Portuguese?
user
I could try. What are some situations you might be encountering?
assistant
How would I say basic greetings like "Hello" and "Goodbye" in Portuguese?
user