Georg Philipp Telemann's '9 Sonaten' are exemplary of his prolific output and accessible style within the Baroque era. These pieces likely feature clear melodic lines and elegant harmonic progressions.
Focus on developing a smooth, singing tone and precise articulation.
9 Sonaten 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.
9 Sonaten is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.