How to solve hard dsa problems?

I come from a well known college,but when it comes to solving dsa problems especially dp and graph , not the eays ones medium to difficult, I go blank . It feels like we have to byheart the solution or come across the problem before to be able to solve it now. Else it’s hukanly impossible. I have given so much of try but frustrated like anything. I am good at grasping things, do lot of innovation at work when it comes to development. But dsa I just go blank. Insee lot of my dumb friends getting into faang but I am stuck in f**in service companies struggling to make a living. An example problem: “Max Subarray Sum with At Most K Elements” Even some service companies and product keep hackerank test and I don’t know why they keep so hard problems.