Cramer's Op. 81 presents 16 etudes designed to develop specific technical skills for pianists. These pieces are valuable for building facility and control.
Focus on clean execution of runs and maintaining rhythmic accuracy in challenging passages.
16 Nouvelles études (Op.81) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
16 Nouvelles études (Op.81) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.