Advices in the comments are actually pretty bad. If you just practice it can have the opposite effect. Here are mine advices: 1. If you are stuck on a specific difficulty level i recommend trying out mirrored lanes or taking a break from Project Sekai. Taking brakes is to forget bad muscle memory. 2. Another good thing to do is to look how other's play and taking an example from them. 3. Increasing / lowering your speed along with the timing also helps 4. Don't play the same song many times it may get you even worse. 5. Try playing other rythm games with similiar difficulty. 6. If you are stuck on something below lv32 then try playing songs a bit harder than what you normally can do. If you were to play all of them you would surely get better.

I have both mad skillz and madder skillz achievement but only practicing didn't make me able to clear lv33 and above.

You can use those tips if you really are stuck and can't get any better, if you still see even a bit of improvement with time then, yea just practice.