The professors might ask you some questions that you already answered to in your composition. In this case, all you have to do is say “As I said in my composition...” and give the paragraph. This will show that you prepared well for the defense, and that you know all the details of your project. Besides, you will not have to invent an answer on the spot.
You don’t have to be perfect or to know everything in order to get high marks. Being honest is always a good idea, so admit when you don’t know the answer. This is way better than trying to find an answer that is not correct or acceptable. If the question is not related to the topic of your project, you can tell them this and promise that you will look into this in the future.
You had time to do this in the text, now you have to give simple answers to their questions. If you must use a term, fine, do it, but make sure that you will explain it for the people in the audience that don’t know the meaning. Try to keep everything as simple as light as possible; they are just checking your knowledge.
You had to make a lot of research in order to write such a good composition, and for sure you remember something from what you’ve read. If you can, try to bring in discussion an author or another paper when you discuss about your own. This is a clear evidence that you took your time to gain knowledge and that you are not afraid to show it.
If you can use a computer and build a slideshow, even better. It will allow you to explain the ideas in a fun and easy way, and you will not have to worry about complicated answers. If you are using a computer, you can also present short videos that are connected to the subject. The audience will be impressed that you put all this effort into this.
You will not be allowed to bring any material with you, but most of the professors will allow you to have a few notes. If you are in a bad moment and you can’t remember anything, just read your notes. Ideas will form in your mind and you will know how to continue the conversation without interruptions.
The professors are not there to make you fail, so stop worrying about every single detail. As long as you trust yourself and your knowledge, everything will go smoothly. If you smile, you will let them know indirectly that you are prepared and that you will face any challenge.