Instead of learning "The boy is eating an apple" as an isolated sentence, you learn it because Nils is actually hungry and looking for food in the story.
If you manage to get your hands on the PDF, you have the "skeleton" of the course, but the creators (Skapago) offer a full ecosystem to ensure you actually learn to speak, not just read. the mystery of nils pdf
For those interested in delving deeper into the world of Nils PDF, the following resources are recommended: Instead of learning "The boy is eating an