"I think you not to 20 years old, to?"
"Is, I not to 20 years old."
("No, I 'm 30 years old." )

I think you are not full 20years old.
yes,i am not full 20 years old.
no,i'm already 30 years old.

I think you are not 20 years old enough,are you?
No,I am not enough 20 years old.
(Yes,I have been 30 years old. )
在英语反意疑问句中,NO表示“是的”；Yes表示“不”

You haven't been 20 years old,have you?
Yes, I have't been 20 years old.
No, I have 30 years old.

"I think you not to 20 years old, to?"
"Is, I not to 20 years old."
("Not, I already 30 years old." )

“我想你不到20岁，对吗？” = I think you are under 20, right?

“是的，我不到20岁。” = That's right. I'm not yet 20.

（“不，我已经30岁了。”）= No (That's wrong), I'm already 30.

I guess you are not more than 20, is that correct?
Yes , I am.
( No, I am thirty years old.)

I think that you are not 20 years old yet, are you?
-- No, I am not 20 years old yet.
--( yes, I am 30 years old already. )

“我想你不到20岁，对吗？”
I don't think you are 20 yet,are you?

“是的，我不到20岁。”
No,I am not.

（“不，我已经30岁了。”）
Yes,I am already 30.