You learn a language by attempting to translate given sentences (cards).
If you cannot translate correctly, the sentence will remain in the Roll until you master it.
After your first attempt at the sentence, the sentence is moved to the bottom of the Roll. It will gradually move up for another attempt. If you succeed on the first try, the sentence is considered learned, you receive your reward points, and the learned sentence is removed from the Roll.
For convenience, when comparing your answer with the target sentence: