The expression
¡Hola! (make the second syllable longer) – Hi! / Hello!
is used for greeting (make the second syllable longer). This word can be used with either your acquaintances or strangers.
To ask “How are you”, we say
¿Qué tal? – How are you?
People usually reply
Muy bien. ¿Y tú? – Fine. And you?
To say goodbye, we say
Adiós – Bye / Goodbye
If something’s wrong, you can ask
¿Qué pasa? – What happens/
To say that everything is ready, we use
¡Ya! – I finished / Ready
To express pain, the Spanish use
¡Uy!
¡Ay!
not ”ouch”.