Welcome!
Here is the secret to better marks according to top students:

1. More Questions Done = Better Marks. Top students do around 10 past papers before the exam in exam conditions.
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2. Identify your weak sections and practice them first: This will feel uncomfortable initially, but you must push through. Practice your weak sections until you feel comfortable.

3. Keep a mistakes journal. Whenever you make a mistake, take time to analyse why you made it. Do not move on to the next question until you understand why you the mistake. If you can't figure out why the answer is the way it is - make a note and ask someone that can help you. After this reflection process, write the question number you got wrong in your workbook or on a note-keeping app. Then redo the question after some time has passed. For example, if you get question 2.7 wrong in Paper 1 2018, write in your mistakes journal: "2.7 Paper 1 2018." Then redo the question after 15 minutes or in your next study session. You must do this because simply understanding
the memo isn't good enough.

Ultimately, it's up to you if you want to do well. Put in the work and you will do well. Good luck!