You can use this
Backup and Restore process to overwrite the contents of a course. This is useful if you imported the wrong course materials, or duplicated them.
Sourcecourse site (usually a previous site).
Include enrolled usersthen scroll down and click
Jump to final step
Restore coursepage. Click
Restorebeside the backup file you just created.
Restore into existing courseand choose
Delete the contents of the existing course and then restore
You may have to search for your course using the window below, select the
Destination course, and click
Include enrolled users, then scroll down and click
Course settingsas the are, scroll down and click
You may deselect items that you don't want in the destination course on this page.
Continueto go to your course.
Don't forget to update your syllabus and assignment dues dates!