Hi,
actual GMAT was another 80 points drop (460, Q33 V20, IR 4)

To be honest, I was panic-stricken and also pretty nervous on test day so I think that might have also added to this score.
To cut a long story short, below my experience from the two important parts.
Quant: This part started really bad. I was able to solve the first 2 questions but then a pretty tough word problem (one of my weak areas) appeared which I had no clue to attack, so after around 3 mins puzzling over this problem I guessed and moved on. However, this particular problem threw me out of my rhythm (all concepts I knew suddenly vanished) and I completely lost my cool during the next 5-10 problems which I mostly guessed or rushed through... The upshot was that towards the end of the first 25 questions I got extremely easy problems which I was able to solve in ~40 seconds and at this point I already zoned out and, what is more, at question 37 I had over 13 mins. left. :/
Verbal: After knowing that I bungled the job in quant and that it was impossible to score ~600, I still decided to give my best in verbal. The first half of verbal I did, in my assessment, pretty good and received pretty challenging SC and RC questions, nevertheless, the second ~20 questions I was out of mental power and also pressed for time so that I ended up rushing through the last 10-15 questions (mostly easy questions to my surprise).
On balance, I was expecting a ~550 score but was shocked to see a 460 popping up... In addition, I had the impression that the questions both in quant in verbal were quite different from what I was used to in my prep (OG, Manhattan and
Magoosh), that is, more confusing and knotty... Can this be true?!?
Fortunately, I received a two months' grace from my business school to retake the GMAT until 1st of September. I really need a good strategy to achieve 600+ now

since I'm confident that my level is on no account in this range (460-540) but rather around ~600+ but due to work (10 hours a day), stress and anxiety I think was way below my level and expectations. Still, can work, stress and some unfortunate guessing explain a 160 points drop in 3 weeks? Do you have some advice for me in terms of strategy and further prep?
Thank you guys!
Btw. I canceled the score!