Can you understand this paragraph I tried to translate :) could you correct my grammar mistakes? Thanks a lot!

When I took the oral exam for Administrative law, I studied for 39 question packs out of 40 packs given, unfortunately I chose the 40th pack that I haven’t studied for so I immediately asked to change the question pack. This time, I was very confident to answer because those were the questions I studied for but the instructor told me that all my answers were wrong. This sent me to completely confused. The extra questions he asked me were even more difficult than the main questions so of course my answers weren’t a bit better. The instructor gave me a 6, minus 1 to 5 because I changed the question pack. But as I estimated if my score was 5 then my final score would be 5.5, it was a bit too low due to the big effort I took to study so I asked the instructor to give me a lower score so I could retake the exam (The score required to retake the exam or retake the class is 4.0). But he gave me a 3, and the final score I got was 4.1. So I couldn’t retake the exam nor retake the same class and had to receive a horrible final score that I couldn’t change. Sometimes I think about me as one of the most bad luck students in Law school bitter laugh.