I get you. That’s what always happens to me. I prepare more than everyone I know, yet I still fall short because of something I can’t control. In my experience, people around me don’t prepare their presentations as much as I do, but they still get the best grades because they’re more eloquent. I wish I could give you advice, but I don’t really have any. Maybe you could talk to your teacher that’s what I do, so at least they give me an average grade instead of failing me. Unfortunately, you will just have to get used to people laughing at you. However, I would ditch your friend. They don't seem like good people