You have to complete every step in the lesson:
When you finish a quiz and submit your answers with the "Check my answers" button, you can click on the "Show my answers" button and then you can see which of your answers were correct and what the solution would have been for your incorrect answers.
Go to My Profile, expand the course with the arrowand in the Statistics column click on the document icon.In the popup window you just have to click on View to see your answers.
When you submit your long/essay answer with the "Check my answers" button, your answer "dissappears", but don't worry, it can be checked later:
Go to My Profile, expand the course with the arrow
NB: When your answers are corrected, you get an email notification. Then, when you look at your answer following the steps above, you'll also see my corrections.
If you leave the page for a longer time while filling in a quiz, your answers can disappear after you submit your answers with the "Check my answers" button.
The icons of lessons/topics/quizzes appear light blue if they are completed.
Not-completed materials (and not-passed quizzes) appear in dark blue.