How do you say “What is your name?” in Korean?

= 이름이 뭐예요? / 이름이 뭐야?

How do you say “How was your weekend?” in Korean?

= 주말 잘 보냈어요?

How do you say “I have to go now.” in Korean?

= 저 지금 가야 돼요.

How do you say “I'm late. I missed the plane/my flight.” in Korean?

= 늦었어요. 비행기를 놓쳤어요.

How do you say “I have come to register for TOPIK. I'd like to be fluent in Korean someday.” in Korean?

= TOPIK 시험 신청하러 왔어요. 언젠가는 한국어 잘하고 싶어요.