Cramer's Op. 37 sonatas offer a mature Classical voice, presenting a thoughtful interplay between melodic content and harmonic development. They are known for their lyrical qualities and well-structured movements.
Cultivate a singing tone in the melody while ensuring the accompaniment supports it harmonically.
3 Sonatas (op.37) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
3 Sonatas (op.37) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.