Try solving 800 level problems with the most frequency, if that too doesn't work maybe try other platforms and get a decent knowledge about implementing stuff using basic arrays and vectors, I personally did a lot of leetcode before coming here, I did it to a point where I could solve medium problems of leetcode decently and when I got here I could do easily 800 — 1000 rated problems.

So I guess it worked for me, you could give it try.