Ok I'm not sure if that's going to be any useful but it helps me tremendously. So usually when I know I'm about to speak I get this almost panic attacks, my heart starts raising like crazy, my breath rate increases and I can't get my words out I just block ( especiallyin English as this is not my first language) But recently I discovered that slow and calm breathing just before I speak helps a lot and for the past few weeks I been noticing significant improvements in my speech. What I do, I start to breath in slowly, then hold my breath for like 1-2 secs and breath out very very slowly. When you do it few times you automatically calm down and your heart rate slows down as well. When it's time to speak I say my word loudly and very clear, make pauses every few words and most importantly I try not to rush. Also, I try to speak confidently and look people in the eyes (even though don't feel confident at all), It's kind of 'fake it till you make it' technique bit it works for me. I'd also recommend practice the presentation at home as much as you can, that way you'll get used to it and thos won't be such massive surprises and stress when you in front of people. Not sure if that's going to be any helpful, but hope it does. Good luck with the presentation and let us know how did that go!