Experienced presenters sometimes leave gaps in what they cover in order to prompt questions. A presentation should fit the time allowed for it. You can only learn this by experience or by rehearsal. Fluent performance is the icing on the cake. A presentation can still make its point even if you are nervous.
Jokes are dangerous.
From everything above, you can see that preparation is essential. Your project supervisor should be present at both your mock presentation and the real thing and will provide comment on your proposals for your presentations before you make them and feed-back after your mock presentation. The mock presentation is a learning experience. Your supervisor is there to support you. Both presentations are opportunities for you to tell some of your fellow-students and some of the staff about a piece of work which is entirely yours and which is something you should feel proud of.