What about if I do know the story, but I know they wanna tell it over, can I answer lying with a "no"?

Listen, this is actually a very important question, and I'm glad you're asking because it shows you're thinking about the halacha carefully. The answer is: you are absolutely allowed to say you don't know a story even when you do know it - and in fact, this is the proper derech, the proper way to conduct yourself. This is not considered lying at all. Let me explain why. When someone wants to tell you a Torah story or a d'var Torah, and you interrupt them saying "I know, I know, I already heard it," you could be destroying something very precious. Maybe this person just started doing teshuva. Maybe all they needed was one student to say "Wow, what a story!" and they would have become a mechanech, a teacher. They would have started teaching people every week and bringing Jews back to Hashem. But you destroyed their confidence by saying "I already know." The magnitude of saying "I know" can potentially destroy millions of lives. Why? Because that person who was about to teach you - you just killed their desire to continue teaching. They think everybody already knows everything they know. Even more - when someone tells you a story, they're actually learning while they speak. It's part of their own growth, their own teshuva process. By letting them tell you the story, even if you know it, you're helping them in their avodah. So the halacha is clear: even if you've heard the story 50 times, even if you wrote a book about it, you say "No, I don't know, please tell me." This is not a lie - this is proper middot, proper character traits. You're giving them the opportunity to teach, to share, to grow. That's a mitzvah. Never interrupt someone's story. Let them finish. Show interest. This is the way of the tzaddikim.