I’m already in year 12 but really want to do sixth form

So currently i’m in college doing a course i’m not really passionate and for GCSE’s i got okay Grades (5’s and 4’s and one 3) but for this ENTIRE academic year i’ve been applying to retake English Language which is the one i got a 3 in and so far NO ONE has gotten back to me even though they read my emails, anyways, i really want to go to Sixth Form in September but half of the Sixth Forms i’ve emailed has either rejected me or said i can apply to their Sixth Form but i didn’t get the required grades for the courses. BUT there was this one grammar school which said i can take entry exams to get in and those exams will be Psychology, Economics, and Politcs and Government (which is the ones i want to do so bad) and also English Language, but i’m really bad at revising and i know for a fact on my own i won’t be able to pass them, so i’m looking for tips, techniques, basically anything. Also even if i do get in i’m also super nervous and anxious because i feel like i’m be left out since i’m really bad at talking to people and i will also be older then the year since i’ll need to retake year 12, i also feel like i’ll be really overwhelmed with doing A-Levels and i just don’t know what to do.