Hi Hans!
You can use the course completion percentage for tracking, and set it to 50%:
When the learner has viewed a specific percentage of the course. This is measured per lesson and is satisfied when the last required lesson is completed. For example, if you have a 10-lesson course and set the course completion tracking to 50%, the completion requirement is sent to your LMS when the learner completes the fifth lesson.
You can find more about this here in this article on When a Course Communicates Completion to an LMS
