Jacob Rosenhain’s 'Bertha' is a sentimental character piece that exemplifies the mid-19th-century salon aesthetic. The piece relies heavily on expressive phrasing and delicate dynamic shifts.
Work on expressive phrasing through the use of subtle rubato to convey the emotional nuance of the piece.
Comparable difficulty and character — good candidates for what to learn next.
Bertha is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 4.
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.
A typical performance of Bertha lasts about 4 minutes.
Bertha 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 Ballade by Jacob Rosenhain, Pavane pour une infante défunte by Maurice Ravel, Bethena by Scott Joplin — see the full similar-pieces list on this page.