Haydn's violin/flute sonatas are mostly arrangements of other works, and the only one considered original is the first one of the set (of eight). This particular Sonata in G (no. 8) takes after the String Quartet in G, Hob. III:81, but it omits the minuet and trio movements.

Sonata in G major - I. Allegro moderato

Sonata in G major - II. Adagio

Sonata in G major - III. Presto

https://musopen.org/music/1147/franz-joseph-haydn/flute-sonata-in-g-after-hob-iii81/