Don't try to blag it. If you don't know the answer to a question in a presentation, simply say so and tell them you'll get back to them with an answer. They'll respect you for it
You will be able. Even if you feel nervous at first, you will feel fine a few seconds after you start to speak and everything you know will be there for you to recall.
What if it all works out? What if you practiced enough that you articulate your words with linguistic prowess? What if people take note of your confident tone and find themselves impressed?