It sounds like you're in a bit of a dilemma. You're interested in both medicine and astrophysics, but you're not sure which one to pursue. You're also feeling behind in your studies, and you're not sure if you can catch up.
I can't tell you what to do, but I can offer you some advice. First, it's important to think about what you're passionate about. Which subject do you find more interesting? Which one would you be more excited to study for the next few years?
Second, it's important to consider your strengths and weaknesses. Which subject are you better at? Which one would you be more likely to succeed in?
Finally, it's important to think about your future goals. What do you want to do with your life? Which career would be more fulfilling to you?
Once you've considered all of these factors, you should be able to make a decision about which subject to pursue. If you're still not sure, you could always talk to a career counselor or a trusted friend or family member.
As for the integrated foundation year in physics at the University of Manchester, it's a great option if you're interested in astrophysics but don't have the necessary qualifications. The course will give you the foundation you need to study astrophysics at university.
If you decide to stick with medicine, you'll need to work hard to catch up. You can do this by studying hard, getting help from your teachers and classmates, and using online resources. It's also important to stay positive and motivated. Remember, you can do anything you set your mind to.