If you get to sleep after 12 am even 30 minutes after midnight why the next day in the morning when you wake up do you feel dizzy and tired and can't focus on studying?

You probably did not get enough sleep. You may want to try to get to bed earlier. If they still persist, you probably should go to a doctor to find out if there are physical issues causing you to be dizzy, tired, and unable to focus. It is likely that getting to bed earlier will solve the issues, though.