감사합니다 is also right.
Are there other ways to say this that I should know about? Informal or formal?
Is gomawo(yo) ok too?
고마워 is used casually. People you're good friends with typically. Resource: Korean husband.
i think so, i heard always on koreans whenever they're talking
This is how I learned it from a native Korean speaker. I think this is an among friends level.
That does not sound right. Is that a super high korean version like Oxford english to everday english? Because I ve never heard it like that in Korea
I'm not sure but i think it's just a polite way to say it like if you were talking to your boss or something
Is there a difference between 고맙습니다 and 감사합니다?
Basically it means the same. 고맙습니다 is pure korean, 감사합니다 descended from Chinese but is often just as much as 고맙습니다
gomabseubnida = thank you (thank you for going to my birthday party)