One of the frequent mistakes of people who learn languages – is to hurry to absorb more and more content during one day. While doing it they get tired and can't find the motivation to proceed to learn tomorrow. It's better to study for a short period of time but every day.
So we made a mechanism that prevents a user from passing more than three lessons a day.
The "Progress" section shows all the course lessons and a user's progress. It motivates a user to finish the course after he starts it and shows a progress. Here I use a gamification technique – show a medal, cup or diamond if a user has a high score for a lesson.