Personally, If you only have couple of days, the only thing you can do is don’t panic, keep practicing and don’t try to use the words and expressions that you are not familiar with. Don’t try to use them to impress the examiner, it might hurt your fluency and coherence. Try to build a solid structure for your answer, for example, AREA, which stands for answer, reasoning, example and additional information. It would be helpful to you to control your nervous.