Having freshly graduated from four tough, nerving years of high school, I'm here to pass on my “expertise” of staying sane.
For starters, it's completely fine to be confused by your surroundings. To be honest, I went through recurring episodes of cluelessness all four years, whether it was joining a new school or simply taking a class I've never heard of before. It was just a matter of me accepting unfamiliarity. I know this is contrary to popular belief, but it's sometimes beneficial to stop trying to figure things out. Just give it time and you will naturally, but slowly decode high school.
You will face a ton of pressure throughout, even if it is meeting new people. It is important that you prepare yourself to be comfortable with situations that are out of your control or comfort zone.
Especially to all the freshman out there, don't rush in trying to fit into the “established” high school mold in your school. It's easy to feel hesitant to change or rush into burning yourself out because of the new pressure of high school, but just relax and ease into the transition.
Trust me, being surrounded by confusion will be alright.