What you are describing is rather vague. If we give you "advice", how are we to know if this is something that you had encountered already and, obviously, is not working.
What you should do is pick out ONE example of a problem that you cannot solve, go to the Homework forum and show what you have done, and then indicate where you got stuck. Then wait for help or queries from other members here.
Once it is solved, see if you've understood why you got stuck, and if you've understood something that you didn't before. Go find another similar problem, and try solving it. If you can, there's a good chance that you've overcome this obstacle. If not, then repeat the above.
Otherwise, we are left with some vague idea that you have problems in rotational dynamics without really any specific information on what really is the source of the issue.
Zz.