"You're not kidding"
Can this mean "What you're saying is true" or "I agree with that" in a certain situation?Yeah, Jura. But it hasn't came across as literal in the situation and then wicked mental translation kept intruding in my brain.
I agree, 엘리자베스. Thanks a lot, Neal!

Question

"You're not kidding"
Can this mean "What you're saying is true" or "I agree with that" in a certain situation?Yeah, Jura. But it hasn't came across as literal in the situation and then wicked mental translation kept intruding in my brain. 
I agree, 엘리자베스. Thanks a lot, Neal!

Answer

The exclamation "You're not kidding!" expresses that someone is in agreement about something.  For instance:

A: "That was the biggest ice-cream I've ever eaten"
B: "You're not kidding! I thought I would never finish mine.

This is different to "You're kidding!", which is essentially an expression of dismay or disbelief, as in:

Person A. Guess what! You have just won a million dollars!
Person B. "You're kidding! I've never won anything before!

Answer

Neal awnsered perfectly nothing i can add really.

Answer

People usually say this when they are told something fantastic. Yes it means, is that true?
Example:
 Person A. Guess what! You have just won a million dollars!
Person B. "You're not kidding?"