They both mean wait, and because they both end in "yo" I believe they are both formal.
It contains a hyphen so you know the two words are connected and so you don't make the mistake of putting 3 cups in instead of 1/3
Well for me, I'm learning Japanese right now. The first thing is to learn how to pronounce their vowels. That's really important and makes it easier to pronounce the word. Also learn how their other letters sound.
Another thing you can do is to watch movies in Korean with English subtitles or movies in English with Korean subtitles.
P.s. I'm learning Romaji so the first tip applies more to Korean in English writing. Example: Annyeonghaseyo
천만에요 :)
