Advice for Holding Down Notes

Hi everyone,

I am learning the Bach prelude from English Suite #3. I am having trouble holding down the top notes in measures #16-20 (and the corresponding measures) while playing the notes in the middle voice. It is especially difficult for me to transition from one top note to another top note without a break in between notes. Also, switching from finger #4 to #5 on the G in measure #19 is a huge issue for me. I have been working on these measures for over a month, but I still have to play the piece rediculously slowly in order to execute the measures smoothly.

I really appreciate your help,
Samuel