Rotating Hand When Playing the Piano?

If you really can't get it ask your teacher for a study so that you can practice the hand movement without worrying about a little test called a grade exam.

You probably need to change teacher as well because the teacher has to be able to explain things in a way that you can understand. Grade exam pieces are also not the time to be learning new techniques. You should have done this before you start thinking about doing tests. Grade exams are little tests to check that you have learned your lessons properly. You can't learn your lessons properly if you have a teacher who doesn't teach you the techniques you need to know before you start on the test pieces and you can't learn your lessons if the teacher can't explain the techniques to you in a way that you can understand.

Please also understand that grade exams are not standards in music so it doesn't matter if you don't take them but it does matter if you don't understand what your teacher is telling you to do and it does matter if your teacher is using the grade exam pieces to teach you new techniques as this is what studies are for and you should be able to already do this before you even think about taking a small test in it.

Proper, structured piano practice helps you stride forwards. Learn here https://tr.im/piano4all

I say ‘proper’ because a lot of people have an idea that practice IS just playing songs over and over. Practice needs to involve unchartered territory.

The golden rule is practice what you can't play, not what you can play

Simple solution... Play slowly.Fix the volume the left hand is supposed to produce and stick with it.You could try playing both hands softly first and then try to play it with the left hand at the same volume but the right hand being louder.