That's a pretty good score you got on the Oliver Lehmann exam, his exams questions are pretty difficult, excellent job you did there.
I can feel that you are a little bit stressed. Spend the day before the exam in relaxation, your mental condition is key to think clearly in the actual exam.
Try to do as many mock exams as you can, and as many source as possible too. Not all the questions in the actual exam are written in the same style.
Best of luck,
Joe