What you want is not supported in standard Moodle.
If you want users to see only their courses, you could activate myMoodle. But then, they have no access to course categories at all.
Hiding categories is actually usually counterproductive, so you should rethink your approach. If you want to separate users, so they don't see each other stuff, you can run multiple instances of Moodle.
Roles and permissions
Courses visible only when enrolled
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