For what it's worth, whatever you do regarding exams, make sure you understand what you are studying. So many people use the BGS database and memorise 1000's of answers, but you'll get a shock when you start the flying part of your course and the phrase "did you not learn that at ground school" will become all too common. And when you start flying outside of your FTO, you'll be glad you studied it properly. Just use BGS to test yourself, not learn the subject. Good luck with your re-tests!