"루피가 방금 어이없어 한게 어떤부분떄문인지 궁금하네요" ( => ..어이없어한 게 어떤 부분 때문인지..)
=> I wonder which part made Luffy(?) shake his head with disbelief just now.
- 어이없다: can't believe it; is over the top, ...
- 어이없어하다: react to something totally unexpected or weird, ...
- 때문인지: 때문 + 이다 + ㄴ지.
- ㄴ지: a connective expressing whether something is true. (집이 이렇게 큰지 몰랐어: Didn't know the house is so big).
- 어떤 부분 때문인지: what part it is in reaction to; which part is the reason for ...
"루피 레드불 소속됐는데 잘 해야지 뭐하냥" => 루피 레드볼 소속 됐는데 잘해야지 뭐 하느냐?
=> What are you doing not showing your best, Ruffy, now that you belong to RedBull?
- 뭐하냥 => 뭐 하느냐 (Most ㅇ at the end of a sentence just adds silliness, so can be ignored)
- 잘해야지 뭐 하느냐 => what are you doing instead of showing your best/all?
- AA야지 BB .. = (why BB? / shouldn't BB) when AA is expected ("나눠 먹어야지 그러면 안 돼").
"우리는 알고있어. 루피가 진다는것을" => 우리는 알고 있어. 루피가 진다는 것을.
=> We know it - Ruffy will lose.
- 진다는 것을: 지다 + ㄴ다는 (adjective form expressing a fact or a quotation) + 것 + 을.
* Note ~는 것 vs ~ㄴ다는 것 are both adjective forms made from the same verb with different connotations.
- 지는 것: "losing" - simple and direct.
- 진다는 것: "that one loses" - more formal/indirect, like a general statement or a quotation, or something conceptual.
(it will take some work to fully understand the difference between the two)