In my humble opinion, these would be useful Japanese phrases I would have in mind:
Goodbye - Sayonara
Yes - Hai (Japanese seem to acknowledge each sentence you say with "Hai")
No - No
Please - Shite kudasai
Thank you - Arigatogozaimashita (Good luck writing this out! hahaha)
I keep hearing "Sumi masen" (I'm sorry) and "kurewa" (living room)
I have Korean and Japanese friends so sometimes, my brain mixes up the Korean "yea" with the Japanese "hai" @_@
I think I shall try to focus on Japanese first because I have been fascinated with Japanese culture since I was 9 years old.
As the Japanese say: Ganbatte ne! がんばって ね