This short fugue is attributed to Bach and demonstrates a solid understanding of fugal construction. It provides a valuable opportunity to study Bach's contrapuntal techniques.
Focusing on the independence of each voice and maintaining rhythmic precision is important.
Allein Gott in der Höh sei Ehr (BWV Anh.48) is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 4.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Allein Gott in der Höh sei Ehr (BWV Anh.48) lasts about 2 minutes.
Allein Gott in der Höh sei Ehr (BWV Anh.48) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.