Are you at?
You don’t learn to give a good speech in school. At school, it is often just a speech or a short presentation in a fixed pattern. You only become a good orator if you gain sufficient experience, or if you immerse yourself in the art of rhetoric.
Your background also plays a role, of course. Did you always have to keep your mouth shut as a child? Or was there a lot of debate going on in the family and were you allowed to have your own opinion? The good news: giving a presentation is a profession. And you can learn a trade!