Once you chose a unit to begin with, you will see a navigation bar above the main resource.
Above the chapters you can see your course progress. Once you made progress in the course, the grey bar will turn to green. When you have finished your unit, you can easily switch between the units with the buttons "previous unit" and "next unit". In the grey bar above the learning resource, you can see if the resource is a main resource or not. You can also see if there is a Quiz available. If the word "quiz" is grey, there is no quiz to this resource. If it's blue, that means there is a quiz waiting to be solved. When all questions are answered correct, the word will turn green.