A. What things make a great movie a great movie? Please explain.

I think the movie's content is the most important. 

And it's also important to cast an actor who fits with the movie. --> Also, it's important to cast an actor who fits the movie.

=> Corrected: The sentences are corrected grammatically. 

B. Make these sentences into English.

아니, 내 것이 아니야.

잠깐만, 저건 뭐니?

잠깐만, 저건 뭐니?

No, It's not mine. (Correct)

Wait, What's that? (Correct)​

Wait, What's that? (Correct)​​