Bach's Two-Part Inventions are didactic pieces designed to develop keyboard technique and contrapuntal understanding. They are distinguished by their clear melodic lines and intricate interplay between two voices.
Developing independence between the hands and a clear contrapuntal line is the primary challenge.
Inventions is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 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 Inventions lasts about 20 minutes.
Inventions is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.