Hi Martin,
based on my experience I would say that even retaking the same exam helped me improve my understanding rather than remembering the right answer. For example, many times gaining a better understanding of one question has helped me answering other questions correctly.
Anyway, my recommendation would be to take different exams first, before retaking the same exam twice... just to be sure you let the newly acquired information sit in your memory, and you do not answer them somewhat automatically, possibly because that question is so fresh in your memory you just get it right with no second thoughts on that.
Another thing that helped me a lot was reviewing the questions that I marked, while answering them correctly. Sometimes I had a feeling one option was the right answer, but couldn't articulate the reason appropriately. So I flagged that question, and try to learn from the explanations provided the actual reason I picked that correctly.
Best of luck for your exam!
Gabriella