These are Schubert's famous settings of poems by Goethe's 'Wilhelm Meister', renowned for their profound lyricism and expressive piano parts. The pieces explore a wide range of emotions and musical ideas, showcasing Schubert's mastery of song composition.
Achieving a singing tone and understanding the harmonic language are paramount.
4 Gesänge aus 'Wilhelm Meister' (D.877) is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
4 Gesänge aus 'Wilhelm Meister' (D.877) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.