This piece is a lyrical and tender Romantic or early Modern composition, likely a song transcription or character piece. It is distinguished by its gentle melodic flow and expressive harmonies.
Developing a warm, singing tone and managing the ebb and flow of melodic lines with subtle rubato are crucial.
Ah, più tremar non voglio (K.71) 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.
A typical performance of Ah, più tremar non voglio (K.71) lasts about 4 minutes.
Ah, più tremar non voglio (K.71) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.