So recently i started doing competitive programming after a break. What I notice from practice or participation in a contest is that, I'm not able to solve B problem in div2 and C in div3 and finally C(sometimes) and D in div4. Are there any resources that contain the topics to solve these problems?

I felt bad for not solving a problem after taking a long time on it(especially div2 B). Could you guys suggest any tips and resources? Also as a newbie , should I spend a lot of time on a problem before looking at the editorial ?

Any suggestions would be helpful! Thanks