You can find all the information about the course workload on the course description page. 

The workload depends on the course and on how deeply you decide to go into the course materials. Some require 2-3 hours per week, others between 5-6 hours per week. 

These are statistics, you know yourself better and you know how fast you can assimilate new knowledge. You know what your weekly and daily schedule is, when you are busy and when you have spare time. 

However, you have no reason to worry about. The courses content and the course activities were designed to make your learning process easy and enjoyable through a relaxed schedule.