should I take a gap year and reset my gcses to do a levels

so guys basically I want to do a levels but there is a big problem which is my grades it doesnt match with the entry requirements so they didn't let me do it obviously but there is a issue that I wasn't here in the uk for about 1.5 years for family issues and when I came back to my school in year 11 they put me in classes randomly like I didn't even choose they put me in business and we didn't even had an teacher or geography which I hate and I'll never understand whatever this is not thing so should I take a gap year and reset my low graded gcses because I really need science and maths I want to computing I have a good grade for that but not enough for the maths and science I also done IT t level as well this year but I don want to do that because I don't like it I want to do something more academic way so should I take a gap year and reset it and then re-apply to college like how do I get the lessons and stuff and do I have to talk this to my previous school, my current college or the college I want to and I applied for (but they said I can't do a levels so im not a student there) what I need to do before its too late im so stressed.