Hello dear friend!
I have been in the same position once. I was really nervous, but everything went fine. If you go around the stage people will think that you are scared, so don´t do that!
If you don´t know the answers or isn´t sure, don´t get scared. Take your time and if you have the opportunity to ask a friend or call someone, do that. Otherwise give it a chans, and hope for the best.
You never know the answer until you try. Remember the worse that can happen is that it´s incorrect, not the whole world!
I think that you will do it perfectly, I believe in you!
Have the best presentation,
Regards
Diana