Stuck between Hard and Very Hard Quant Questions

Best suggestion I can make is to hone ur skills(practice, practice and practice) and make sure you know the fundamentals (Bunuel seems to have covered pretty much everything you need to know in his signature, check it out)
Sometimes very simple things can sway your way of thinking or confuse you to the point where you have to guess things(and get them wrong 80% of times), for example, something like 0! = 1 or the fact that 0 is an even integer. Alooooot of times in DS questions you will end up getting an answer wrong due to being unaware of pretty much basics.
Also its worth mentioning that you really need to pay attention to the details of the question. Alot of times you will see traps that will lure any inexperienced person into them, thats veeery common in PS questions I'd say. And another thing, really really pay attention to the numbers you are working with. If its integers or primes or any numbers, that aswell is sometimes a killer.
For instance, a question where its asked whether integer X is greater than 1 and then you get a solution in a given inequality: (x < -5) or (X > 4 and X < 5), you should not get tricked by that positive part because u are asked about integers and that part contains 0 integers.
I wish you luck and I hope I helped at least a litle bit.