Second attempt failure

About one year ago I decided to take the GMAT to make it into my desired master's program which is International Management at Tilburg University in the Netherlands. In October 2019 I started studying for about 10-15h per week and continued to do so until December. The last 2 weeks before my .exam I studied full time. I took two practice tests during that time and since I scored 540 on the first and 570 on the second, I was not really expecting to actually make the 600 on test day. On December 28 I took my first Gmat attempt and I scored 590 (Q:38 V:34). It went better than expected, I felt that my concentration that day was just on point. I decided immediately that I want to give it another shot since I'm so close to my goal.
I felt like I should focus more on math since my verbal score seemed to be solid. In the end I ended up buying the Magoosh GMAT package because it offers you a 50 point score increase guarantee. I couldn't study for the GMAT in January and February because I had to take exams but I started again in March and planned a second attempt in May. I worked through everything in that Magoosh prep course, I watched every video and I did all the practice questions they offer. Because of Corona the test centers were closed in May and after reading the bad experiences with the online whiteboard I didn't dare to take the online GMAT. In the end of May I took a prep test from Manhattan and scored 590 (Q:42 V:31). Since I had technical problems during verbal which made me lose 5 min of my test time, I didn't worry too much about my drop in that score and was happy about my increase in quant. I felt ready to take the test for the second time.
2 days ago the test day came and I felt confident that I'll get those 600 points that day. I was definitely nervous but overall I felt good.
The test started and during verbal I already had a slight feeling that the questions I'm seeing are easier than the ones I'm used to, especially the RC. I finished the section with 9 min left on the clock. Then I started with quant. I couldn't come up with a solution for the first question, even though I knew it was an easy one. I went through with the section but the questions were so much easier than ever before. After finishing that section I was already worried that I probably didn't get the 600 again but when I saw my result later I was more than shocked:
530 (Q:31 V:32).
I couldn't believe my eyes.
I have no clue what went so horribly wrong that day but I have to find out asap. I only got one more chance to retake in about 3 weeks to get the score on time and I really don't know what to do anymore. Does anyone have any suggestions what I could do to improve?
I bought the enhanced score report and you could tell that I was doing bad overall, but what stood out to me were the following insights:

- verbal sub section rankings:
CR 78th - Analysis/critique 66% / Construction/Plan 100%
RC 9th (????? I felt like all my RC's on the test were way too easy) - Identify Inferred Idea 60%/ Identify stated idea 40%
SC 72nd - Grammar 57%/ communication 100%

in the first quarter I had only 50% of the questions correct, in the last 88%

- quant:
Geometry 33%
Rates/Ratios/Percent 60%
Value/Order/Factors 54%
Equal./Inequal./Alg. 80%
Counting/sets/series 100%


Does anyone have any tips to help me raise my score within the next 3 weeks to a 600?
Thanks in advance!