It pretty simple to explain: you breathe in for 4 seconds, breathe out for 7 seconds and repeat this 11 times. My therapist told me about it and it works kinda well. I feel you so much, I don’t know how old you are but I’m 24 now and it got better over time by just forcing myself in situation I would rather want to avoid. And I’m sure this can help you as well, an university is the perfect place to practice, you will be confronted with a lot of different people and tasks and it’s not the “real” world. It’s totally fine to fuck an presentation up because it will have no impact in your life