This is “The Skaters’ Waltz,” written by Emile Waldteufel and arranged for four hands by J. Park. There are two versions, one in the key of C major, and the other one in the more difficult key of A major. Play it with a classmate. A goal of the project is to learn the duet well enough that you can really listen to and evaluate what you are playing.
Various seventh chords are applied for the second part (the lower part) instead of the basic triads. Adding of the seventh chords subtly enriches the waltz. See measures 11, 13, and 15, for example, to understand how the seventh chords harmonically change the piece.