You can restrict users to their own contents using the new update for the Roles feature in LMS. This feature allows restricting new contents that are created on or after April 15, 2016. All other contents created before this date cannot be restricted due to the nature of granular permissions.
Roles comes with 2 different permissions for courses, contents, tests, and live classes.
This is the default option and it allows everyone with 'super admin, and 'teacher' user type or users with specific permissions to see each others content.
This option permits restricting users to see only their own content.
You can edit existing Role and change these options or create a new one.