I know I'm a bit late, but better late than never
You need to use two different tables: one for authentication and another one for enrolment.
The reason is the authentication code expects the user table has only one row for each user, with all the details for that user, but nothing related to courses
Then you have a separate table with the enrolment data, where you can have as many rows as you need for any user (in fact, you'll only need the user 'identifier' in this table).
Saludos. Iñaki.