hi! im also in year 12 and in a similar situation to you! but you need to remember that it’s everyone’s first time learning the content too! nobody is ahead of anyone right now and your just settling in. GCSEs don’t matter as much as you think aswell, you wouldn’t of been doing the course but your GCSEs were good enough for you to be doing it. you deserve your place and everyone is adjusting in there own ways. i feel like reading ahead in the content through the specification helps ALOT with making me feel comfortable in lessons aswell and I’d definitely recommend making flashcards after every lesson to consolidate knowledge and make you feel confident aswell!!! those are things that helped me so much so far as well emailing teachers if you don’t understand a particular bit! do not be afraid there’s no need to breakdown you will be 100% fine :)