This is an opera by Schubert, and its piano transcription likely captures the work's dramatic sweep and profound lyricism.
The main technical challenge is navigating the complex harmonic language and conveying the operatic drama through nuanced dynamics and phrasing.
Alfonso und Estrella (D.732) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 8.
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.
A typical performance of Alfonso und Estrella (D.732) lasts about 15 minutes.
Alfonso und Estrella (D.732) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.