The first movement calls for a dignified performance. Clearly differentiate the contrast between the orchestral and solo sections. Following this, we address the tempo.

In fact, while recordings of this piece are scarce, there is a recording played at approximately quarter note = 94, but this might be slightly too fast.

For the tempo of this piece, choose a tempo where the 32nd notes appearing throughout the piece do not sound rushed. Avoid a tempo that is too fast, leading to poor articulation where it becomes unclear what notes are being played.

Naturally, the tempo should not be reduced in measures 37-40. Here too, select a tempo that allows for comfortable playing.

Author's Discretion

This concerns measure 31, specifically the issue between beats 3 and 4. I am convinced that this is a misprint. I believe that the first note in the right hand on beat 4, which is written as C#, should actually be C. While it might be a leap to suspect that the C on beat 3 should actually be C#, in that case, the C in the left-hand chord would also need to be changed to C#. Having listened to a considerable amount of Bach's music, this passage clearly appears to contain some kind of error. If it were me, I would correct the C# on beat 4 to C and perform it that way.