Public speaking isn’t so much knowledge, or intelligence – it’s familiarity and experience.
You can take a person with 10 public speaking appearances and put him up against at person with 100 public appearances and it’s usually no contest. Just take your lumps and move on. Ten years from now you’ll be a professional – nobody will touch you.
If you are really into public speaking, look up your local Toastmasters and go to work. (I didn’t, but my dad always gave speeches and said that was his best advice for people that wanted to do that sort of thing.) They tend to place importance on time management and thought organization… among other things.
Good Luck.