No matter how many exercises I do or how much time I spend on a document, why does my level not change?

To see a progression in your general level, you must pass the comprehension tests offered at the end of the 7Speaking activities. Studying a document for a long time without completing the comprehension test does not change your level.

Vocabulary and grammar quizzes, and the time spent on a document, do not impact the level, they only serve as practice exercises.