Ava Maria

This is a J S BACH / C F GOUNOD version.
I am I believe playing it as the music score but it appears to be different to how you normally here it being played. Am I doing something wrong. A local church organist friend tells me I am playing it as it is written. Its my first upload and also I am new to the Organ Having recently taken it up Via Hauptwerk to try to keep my mind active having taken early retirement