If you download it on an Android it requires 71 MB, and on iOS the app needs 75 MB, which changes with updates and the downloading of audio and video files.

The application saves the learning content to the device’s memory, which you can clear out by clicking on the More -> Clear cache option.

Your profile and your progress will stay as it is regardless of this, you don’t have to worry about those because they won’t be lost. The application deletes only the data which is not used. If you complete an older lesson, then the app downloads the data belonging to you again, which won’t affect your user-experience.