I took AP Bio last year and got a 5. It was my first AP class (along with another), and I was also the youngest person in that course, so I think I can kind of understand your situation.

For preparing for it, I'd just say to read and finish an AP prep book during the weeks leading up to the exam. It's just a surefire way to make sure you know everything that's needed, no matter how awful your teacher might be.

Another thing I'd recommend is to find an exam repository (you can find some on this subreddit, though they can be kind of elusive if only because most are password-protected and the OPs only respond to messages for a period of time).

I didn't time myself or simulate any sort of testing environment lol, I'm lazy. But I think I did go through ~5 of the past exams or so in the week leading up to the exam. Just do as many as you can and take the time to really read the answer key and understand how they mark stuff, especially for the written questions.

I think I'm just giving general AP advice in this comment, haha. I guess my point is that there's nothing special about AP Bio that makes the preparation for it any different. There's a little more memorization required than usual, but even then it hasn't been much since they made changes back in 2013 or so.

Tl;dr it's not hard, read prep book and practice on past exams. Have confidence in yourself.