1. Microsoft PowerPoint for PC, Keynote for Mac. Chinese people aren't that much different from everyone else on this planet.
2. And again, Chinese people aren't that much different from everyone else on this planet. We use slides and stand in front of everyone to give presentations too. Surprisingly.
a) 当你在演示课件时 / 当你在进行演讲时 / 当你在演示PPT时
b) 你是演讲人
I hope this helps.