I have a courses site where students take online courses and then take exams and get their certificates.
The courses content type has an entity reference to "Lessons" content type which has a further reference to Exams content type ( Webform).
The progress of user is being stored in a custom table in database.
Now we need to build a native mobile app with login / registration, and taking courses and exams features. (user registration / login and progress should be synced with site database)
Any ideas to start with? Custom API, web services or reading and writing to database directly.