There is no course. Your next lesson doesn't exist until you finish this one — it is written from what you got right, what you got wrong, and which of your words are due for review.
Three things feed it: grammar you struggled with comes back, words you've met return on a spaced-repetition schedule, and new material is drawn from a fixed catalogue of skills, in order. That is also why two learners never see the same lesson.
There is one lesson a day, and that lesson is the whole day's plan. It is sized to your daily-minutes goal — a bigger goal means a longer lesson, not more lessons.