How can I do better in A2 level Biology exams?

I was about the same in school, if the exam was oral I did much better than in a written exam, since in a written exam I left half the stuff I knew out, since I didn't know that was asked too.

I can't really tell you a good strategy, but tell you that it never held me back from anything, probably because it turned out to be more important to do well in oral exams than written exams for me. And I think I figured it largely out.

So I would think practice is the thing. The problem is that you need somebody to check your answer and tell you where you are going wrong. You could ask your teacher if your teacher might be willing to help you. Since it sounds like you are generally a good student, the teacher might be willing to do that.

Alternatively you could see if there are some other students who might be willing to form a study group. Then you could practice all together.

Another option might be to pay somebody more advanced and who is a good student in that subject to help you.

You obviously don't have any problem learning the knowledge, just applying it to the question. So you have to practice getting the hand of understanding the question.

I guess you also could try out biology books which have a question section at the end of each chapter and provide the answers in the appendix. Then you could self-check whether you got the question. Though sometimes those questions are rather strange and the answers not the best ones, but generally they are not too bad.