Don't get too hung up on mistakes in speech and composition. The main thing is to show yourself as the best essay writer and expert in the topic under discussion, and articles and verb forms are the tenth thing.
But no. Speech blots, incorrect intonation, too fast or slow speech rate and pronunciation, like the Russian villain from a Hollywood movie, greatly affect the final score. It's cool if you understand the topic, but when you present it in clumsy English, the overall impression is greatly spoiled. You need to work on intonation and fluency of speech, otherwise the examiner may not understand you so well or not at all. In order not to pause in conversation, it is enough to read aloud for 5-10 minutes every day. In addition, do not miss our articles and watch the video to reduce the number of mistakes in the language - some bloopers are very often made even by native speakers, but with a proper amount of practice, you can get rid of them.
In the writing part, too, you should not allow blunders. If you make one mistake in each sentence, you will definitely not see more than 25 points. Typically, students stumble over articles, punctuation, the difference between that and which, the use of the gerund and the passive voice.