Here is the score (p. 34-35). The tempo is Adagissimo. Therefore, play this piece super slow. Notice how the upper two voices create sigh-motives throughout the chorale prelude (two legato notes in step wise motion).
As you play, listen to the lush chromatic harmonies and aim for legato touch with multiple finger and pedal substitutions. Articulate after the second note of the two-note group.
If you are not advanced player, play separate parts of this piece.