Most people who stutter, the stutter comes from the anxiety before starting to speak. So usually things that are scripted are easier to do. What helped me out was that, i used to listen to songs and try to sing w them, specifically rap or any like fast songs. It gets you more comfortable with words and specially rhymes which i think i stuttered the most on. And for the presentations, i recommend writing everything you want to say down and practice it over and over. But when you present, only have reminder cards at most. Good luck.