"Does he understand Mara?"
Have you read the Tips & Notes? Duolingo has hidden the Tips & Notes I want to make sure you know about them and where to find them. If you have not been reading the Tips & Notes, you might want to review those as they contain many helpful details about the language and the lessons.
If you are doing the course on iOS or Android, you cannot currently access the Tips & Notes through the app. To access the Tips & Notes, you will have to access the course using a web browser at https://www.duolingo.com/. You can still do it on your mobile device, but you will have to use the web browser instead of the app (or you can do it from a computer). When you click on a Skill, it will expand to reveal a Start button, a key, and a light bulb.
If you click on the light bulb it will reveal the Tips & Notes and give you a detailed explanation of the grammar that is introduced in that Skill. If you have questions after reading the Tips & Notes for any Skills, then please return to the forum to ask your questions.
The tips and notes for this unit are at https://www.duolingo.com/skill/kl/Useful-phrases/tips-and-notes.