How to fix social anxiety?

I don't know why I feel nervous around people, especially in school and in public. I know the people around aren't paying attention to me, but I still feel anxious. Even on google meet doing a presentation, I feel nervous. My mom says that I just need to talk more and go outside more. I talk with my friends a lot over text but I'm nervous around them in person, I want to say something but I can't.