Just practice the type of problems you want to master. For example,if you face problems in Div2 problem B just filter out the div2 B problems and practice a lot of them. You can use codeforces filter or the problemset to do so. Just practice practice and practice. And also dont spend much time on the easy ones .If you want to reach 1200++,practice at least 1200 rated problems. It will be difficult to start with but have patience.Enjoy cp!!!

You have solved so many problems rated 900 and 1000. Usually, you don’t need to solve that many problems at those levels. Now, start focusing on solving problems in the 1100 to 1300 range and get comfortable in this range.

Besides, you can follow the TLE Eliminator Sheet.

With 700 submissions, you yourself should have pretty good idea, where are you struggling.

Looking at your submissions, there is a pattern, where you quite often solve easy tasks only after a few attempts. If you manage to solve them at first attempt, you'll have more time remaining for more difficult tasks with higher score. I'd focus on that, getting correct solutions at first attempt, that is handling all the edge cases correctly etc.

You solved 124 800 rated problems, 104 900 rated problems and 91 1000 rated problems, but only 8 problems in 1100 or above. The dedication is massive. But Div 2 B's are around 1000-1400 rated, mostly 1100-1200. It's quite expected that you are stuck at B's, you really didn't train for them yet. If you keep putting in this effort but into harder problems you'll advance at a rapid pace. Good luck!

same situations I am faceing now. But now i decide to solve 900 to 1200 rated problem.

Solving 1100-1200 rated problems worked for me

you can also check out this blog if you relate — What Happens When You Do CP Without Discipline

https://mirror.codeforces.com/blog/entry/144595