거라구요

I'm telling you, it's…

→ 것
phrase Uncommon #13,859
I'm telling you, it's… A colloquial, emphatic way to insist that something is the case; the exact translation depends on what comes before it.
KO: 그건 위험한 거라구요.
EN: I'm telling you, it's dangerous.

저건 내 거 라구요!

That's mine!

— 피케이: 별에서 온 얼간이 (2014)

난 죽을 거 라구요

I’m telling you, I’m going to die.

— 라라랜드 (2016)

잘 될 거 라구요

I’m telling you, it’ll work out.

— 라라랜드 (2016)

엄청 멋진 거 라구요

I'm telling you, it's really cool.

— 라라랜드 (2016)