Hello drownedbd, and welcome to the forums.
Next time, please give your thread a title that tells us something about your question. For example, you could have called it "Let me tell you" or "Quite sure it's not."
Also remember that capital letters are an important part of correct English.
Regarding your question, I think we need more context. What are the two people talking about? One person said the first line and then the other person said the second? The second line (Quite sure it's not) does not seem to be an expected response to the first, so it must be referring to something earlier in the conversation.
Student or Learner