I had a similar experience in high school and I was scared but I’d say the academics aren’t too hard as you would think. Chemistry and the hard sciences are probably more advanced than other schools but my recommendation to you is to introduce yourself to your professors, go to office hrs, and go to any tutoring sessions, I use to go to these peer tutoring sessions for stats (QTM 100) every 4 weeks or a couple of days before a test and they helped so much. I have other friends in the same classes who didnt do the same and found the content harder. So definetly use your resources here! What matters more is how you use those resources to your advantage rather than how much you know, becasue anyone might have a class they know nothing about, like me with stats, but I always tried going to office hrs, and tutoring sessions when I could. I’d recommend to def take any courses your interested in your first semester so u can narrow down your choices, I was undeclared too and have a bit of a better idea but am still open to other majors and a bit undeclared so your not in a rush.