Kirnberger, a student of J.S. Bach, wrote this work with a strong emphasis on contrapuntal clarity and precise musical rhetoric. It is distinguished by its strict voice leading and typical Baroque stylistic markers.
Focus on balancing the voices while ensuring precise execution of the Baroque ornamentation.
Comparable difficulty and character — good candidates for what to learn next.
Allegro in D major is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 5.
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 Allegro in D major lasts about 2 minutes.
Allegro in D major is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Allegro fürs Clavier by Johann Philipp Kirnberger, Ballet in B major, EngK 82 by Johann Philipp Kirnberger, Allegro in A-flat major, EngK 50 by Johann Philipp Kirnberger — see the full similar-pieces list on this page.