Hi,
given the time on a daily basis, you can effort to study and optimize your results, 3 weeks should be more than enough to manage that.
What you need to do is, analyze your results thoroughly and figure out where your weak spots are; why you do answer wrong, and also why you do answer correctly.
Then focus on those knowledge areas where you identified your white spots, repeat and deepen the stuff and do some mock exams at this area again.
By following that sequence your results should improve over time.
If not, you should postpone your exam date and we need to talk again ...
Regards,
Markus