I finished the course

I finished the all chapters but I don’t start the course in right time.
So I lose the due date for chapters 1 and 2
But I finished the final exam with the full mark (my grade is 50%) why I’m fail and don’t get the certification

There is an intro video in week 1 explaining how grades are calculated.

Your final grade is composed of 50% for Final exam and 50% for the Labs. To pass the course you need 65%. So, only passing the Final exam or the Labs is 50% of your grade.