To change the duration of a course that has not yet been scheduled, in case there should be no financial consequences for the student, it will simply be necessary to enter the course tab by clicking the edit icon on the relevant row, from the list of courses (Didactics → Collective courses o Didactics → Individual Lessons).
Then, scroll down to "Course Duration.", it will be possible to: move the end date of the course forward or backward; increase/decrease the number of lessons; increase/decrease the number of hours of instruction. If necessary, it will also be possible to change the type of course duration (e.g., from total hours to number of lessons)
On the other hand, in the event that the change in course duration results in economic impacts on student enrollments (e.g. decrease the price if the course duration is shortened, or increase the price if the course duration is lengthened), it will be necessary to change the cost amount directly from the individual student's enrollment order (click here for the wiki article on modifying issued orders)
In case you want to change the duration of a course for which you have already planned the calendar, you will be able to do so only if you have chosen "Manually set or until the end of the academic year" as the duration of the course; in case of "Predetermined number ofhours" or "Predetermined number of lectures" instead, you will have to go through a different route (click here to read the article "Changing the duration of an already planned course")