A couple of things.
Most Christians don't believe in God/Jesus/the Bible, etc. based on reason. They believe based on how they were raised, on weekly reinforcement, and a community that never challenges beliefs. When confronted with a challenge, it often hits them emotionally as if you're questioning their values. There's really no getting around it, but you should at least be aware of how it will hit people initially.
Second, Christians often don't "play fair" in these sorts of dialogs. I consider the three pillars of apologetics to be lies/deception, logical fallacies, and emotional manipulation. Beware of these tactics and call the person on them. They're all admissions that they don't have anything better to give you. In your case, they're attacking you based on your age (logical fallacy) and making you feel childish (emotional manipulation). The other things they're telling you are much the same thing. You're clearly hitting a nerve.
Next, you will likely not "convert" anyone. For most people it takes 7-10 years of really being interested in the truth to come out of religion. You can plant seeds of doubt, ask questions, and point out how silly things look to you.
I recommend you learn about the many logical fallacies and learn to recognize them. Common ones are "ad hominem", "argument from ignorance", "argument from popularity", and "false dichotomy". Start there and expand your toolkit.
Finally, you can end the conversation whenever it no longer benefits you. I usually continue as long as I'm learning something. Not everyone can be reached.
Good luck to you.
