Discover the biggest secret to success for an English Oral Exam
Change your emphasis from what you are saying to how you are saying it. Allow me to elaborate.
Most people think the way to get a good score in an oral exam is to impress the examiner with your answers. This is totally wrong. You will impress the examiner by expressing mistake-free English in a coherent and clear manner. Let me let you in on another tip: the examiner is not looking for totally original and wise answers. It is not the place for it. You don't have the time nor the subject matter to do it.
So instead, focus on being able to say less but say it perfectly. Now, this may seem like a step backwards but firstly, I am not saying only speak basic English but speak, let's say conservative English. So only use the structures and words you absolutely know and forget the rest. The oral exam is not the place half remember a word and use it wrong. So, you need to find that balance between basic English and conservative English. Secondly, the examiner does not really care what you say but rather how you say it. I mean they can only ask you a limited set of questions so they have probably heard it all before.
Take a second to think about it. Which seems better to you: someone who speaks a little conservatively but makes no mistakes compared to someone to tries to use vocabulary and structures that they have not yet mastered and therefore make mistakes?
So that's it. Told you it was simple. Just change your focus from what you are saying to how you are saying it and reap the benefits.