그건 내가 할

that's what I'll…

→ 그것+은
phrase Rare #20,035
that's what I'll… This is an incomplete phrase. 할 means “will do” or “will [verb]”; the following word can change the meaning, as in 할 말 (“what I have to say”) or 할게 (“I’ll do it”).
KO: 그건 내가 할 일이야.
EN: That's something I'll do.

그건 내가 할 말 이야

That's my line.

— 브로커 (2022)

음… 그건 내가 할 말 인데??

Um… shouldn’t I be the one saying that?

— 주토피아 (2016)

그건 내가 할 말 인데??

That's what I was going to say though??

— 주토피아 (2016)

확실히 그건 내가 할 말 이네.

That's definitely what I'm saying.

— 주토피아 (2016)