Possible in less than five months in my opinion, but it all depends on you. I also had extenuating circumstances near to my exam and had awful predicted grades but was able to achieve As>> in the end when I finally got myself together. For me, what helped a lot was doing topical questions. A lot of the exam questions are repetitive, and even if they're different, they're usually the same content, just worded differently to throw you off. Refer to your syllabus and make sure that you understand every single thing it lists on there.
Past papers (try different exam boards as well). These will help you get familiar with the kinds of questions they ask and the mark scheme will help you understand what specific points and key words are necessary to include in your answer. Additionally, you'll be able to figure out what topics you're strong in and what topics you're weak in. Then, start drilling the topical questions for those weak links until you iron everything out. Afterwards, I'd just alternate between past papers, reading and understanding. Teaching people even if not seriously can also help a lot. If you're able to explain something then you're able to understand it, so if you're stuck, just try and explain it and sometimes it'll light a bulb in your head abt whats not clicking. Try to create a sort of chapter plan for yourself per day so you can feel like you made progress with small goals, and to also make sure that you'll have completed all the content you need to work on by the time the exam comes around. Good luck!