Is 2 mgs lorazapam a good dose for presentation anxiety ?

High dose for that: Unless you're extremely anxious -- or are already habituated to Lorazepam at that dose -- 2mg might result in drowsiness and slurring your speech. If you've never used Lorazepam before, a lower dose might be better. I cannot advise you though, since you haven't shared your inner state or any other medications you might be taking. Cbt with a psychologist can help without drugs at all.

Lorazepam: A bit high. Recommend lower dose of 0.5-1mg. , if already prescribed.