Because I’m afraid of making a mistake, or forgetting English words when I’m nervous, and there are a bunch of people in the class that make it harder to speak.
Because I will be afraid of making mistakes or forgetting English words when I am nervous, and it will be more difficult for a group of people in the class to speak when listening
Because I'm afraid of making mistakes, or I forget English words when I'm nervous, and there are a lot of people in the class who can't say it when they listen.