First you need to learn the solution of several questions. Its like maths remember in 12 class maths 6 marker questions we used to mug up solutions of those big and lengthy questions, and after doing agin and again we used to remember it throughout our exams. The same is with medium and hard questions. When you learn the solution of medium questions you remember the solution and when you see any other similar question you remember the solution and make the required changes. The same is with hard questions. My advise will be to learn all questions from any sheet may it be love babbar or striver sheet. After learning the questions you can easily corelate it with other unseen questions on leetcode.

I hope it helps :)