Do I have to complete a course before I can choose a new one?

A Babbel subscription gives you access to all courses in your chosen language. You can change your course whenever you like.
At www.babbel.com, the different courses can be accessed via Courses in the main menu – just choose a new one and click on Set as course. The new course will then be the one that shows on your Babbel homepage.

With an Android or iOS app, you'll find Courses in the app's menu.