The total session hours required to achieve one level of competence varies from student to student. It depends on your commitment to learning and practising consistently. The more you commit to learning and practising, the faster you achieve one level.
For example, a student who spends 5 – 10 hours learning in a week without rescheduling or cancelling class and practising every day outside the class will have a bigger chance to achieve one level within one or two months. However, a student who spends less than 5 hours learning in a week will need a longer time to achieve one level, probably 3 months or more.