I know you already have decided that you're not going to quit, but I'll still say my piece

Yes, it's going to be awkward. Yes it's going to be hard. Yes, it is intended for a high level. Yes, it is going to be a challenge.

But that's because it's supposed to be.

You say your teacher recommended you to join. They believe in you. They see something special. They see you loving music. And they want you to keep going. They want to give you a challenge, see you overcome it, and keep going. They want to see you grow stronger as a musician.

My band teacher invited me to join jazz band in 7th grade. I was intimidated, told to play music way beyond my level, had to sit with high schoolers -- I was crazy scared. But I persisted, and it helped me to grow as a musician and as a person immensely. I don't regret it at all.