During the Classical era, polyphony went quite out of fashion after being the principle approach to texture in the Baroque period. Commissioning patrons wanted music to have clarity and this is why Haydn and Mozart's catalogue is particularly homophonic .

Beethoven often produced similarly homophonic textures in his music and this sonata is no exception.

At the start of the movement, the texture begins homophonically. You could also describe it as chordal. This allows the melody to come across very distinctly with the accompanying parts purely there for harmonic support.

During the quick tempo, a better description of the texture is melody and accompaniment, This is because the rhythm of the two hands isn't the same. The right hand very clearly has the melody with the left hand playing a less prominent accompaniment.

There are also flashes of monophony when the left hand cuts out e.g. bar 10. This also happens at the end of the development just before the recapitulation starts.

There are no passages in this piece that can be described as polyphonic.