im losing hope

Help. If you don’t want to read all this because its long please just read the last paragraph where I have summarised everything

so I'm year 13 and I feel as though I've ruined my life by not doing any work in year 12. I do biology, chemistry and maths and got ADC predicted grades, in that order. I know people say your grades aren't the be all and end all, but for me it is. I've never really wanted much from life other than to do dentistry.

My plan for now is to just focus on my A-levels and get A*AA/ AAA so I can apply with achieved grades next year. But my question is am I being delusional? For thinking that I will be able to improve so drastically in less than 6 months? Especially considering the fact that I haven't really built the discipline previously?

Is it possible to do what I have stated above about getting A grades? I keep hearing people say it is but u need to work hard. Can someone please clarify what exactly they mean? How many hours per day? And im not sure how to feel about this saying because it could just be 0.03% of people who improve by that much.

For background info, I got pretty much all 8s at GCSE with about a 3 weeks worth of intense revision. So basically what i'm saying is I never really had to try so hard and cramming worked fine for me. Come to find out, A-levels proved me wrong. I dont think I’m stupid academically but not revising was definitely a stupid move.

I also need help with HOW to revise for maths and especially chemistry.

I may seem a bit crazy rn but this has been having a tremendous effect on my mental health. And i've never had bad mental health before so I don't even know how to deal with it.

Summary: I do bio, chem and maths and have been predicted ADC but I need A*/A grades. Im in year 13 and have about 6 months. I need to also redo all of AS as i didnt work hard in year 12. Is this possible? Did you/ do you know anyone who has had success? How did they do this?

Help. If you don’t want to read all this because its long please just read the last paragraph where I have summarised everything
so I'm year 13 and I feel as though I've ruined my life by not doing any work in year 12. I do biology, chemistry and maths and got ADC predicted grades, in that order. I know people say your grades aren't the be all and end all, but for me it is. I've never really wanted much from life other than to do dentistry.
My plan for now is to just focus on my A-levels and get A*AA/ AAA so I can apply with achieved grades next year. But my question is am I being delusional? For thinking that I will be able to improve so drastically in less than 6 months? Especially considering the fact that I haven't really built the discipline previously?
Is it possible to do what I have stated above about getting A grades? I keep hearing people say it is but u need to work hard. Can someone please clarify what exactly they mean? How many hours per day? And im not sure how to feel about this saying because it could just be 0.03% of people who improve by that much.
For background info, I got pretty much all 8s at GCSE with about a 3 weeks worth of intense revision. So basically what i'm saying is I never really had to try so hard and cramming worked fine for me. Come to find out, A-levels proved me wrong. I dont think I’m stupid academically but not revising was definitely a stupid move.
I also need help with HOW to revise for maths and especially chemistry.
I may seem a bit crazy rn but this has been having a tremendous effect on my mental health. And i've never had bad mental health before so I don't even know how to deal with it.
Summary: I do bio, chem and maths and have been predicted ADC but I need A*/A grades. Im in year 13 and have about 6 months. I need to also redo all of AS as i didnt work hard in year 12. Is this possible? Did you/ do you know anyone who has had success? How did they do this?