Lay on the floor with your stomach facing the floor. Keep your feet parallel and slowly rise one leg up into a low arabesque. Think about your alignment. This will teach you how to properly engage your back muscles and get your arabesque higher.
There are many exercises to strengthen your back.One of the is lie downwith your belly touching the floor and then try to rise yr head and upper backwithout using your hand ,just bend yr back.Another is lie down as before and rise your whole legs.Te legs should be streched and closed.a third one is lie down as before and rise your left arm and right leg or the right arm and the left leg