How do you say "You're very kind" to someone who just gave you a compliment?
In English, the conversation would be:

A: I think you're really smart and beautiful.
B: Thanks. So kind of you to say that.

Thanks!

Question

How do you say "You're very kind" to someone who just gave you a compliment?
In English, the conversation would be:

A: I think you're really smart and beautiful.
B: Thanks. So kind of you to say that.

Thanks!

Answer

A: I think you're really smart and beautiful.
B: Thanks. So kind of you to say that.

We usually don't say "... kind of you to say that" in this kind of situation.
The conversation might go as follows.

A: X 씨는 정말 똑똑하고 아름다우세요.
B: 아 뭘요, 그렇게 봐 주시면 고맙죠.  (뭘요? is like "What's that?", or "Not really", sort of a light denial)
(alternatively) 아 그래요? 그렇게 말씀하시니 감사하네요. (그래요? = "Is that right?", or "Really")