For starters, there seem relatively few opportunities when the Whippet is in the right 'head zone' to learn. Then, when he does engage in the lesson, he quickly becomes bored and tunes out again. Indeed, training a Whippet has taught you a whole new level of patience and meant you embrace small improvements with the sort of enthusiasm you once reserved for a complex trick with a GSD.
Anyhow, the good news is you and your Whippet are getting there.... albeit slowly.
To successfully obedience train a Whippet means taking advantage of their more lucid moments, and engaging in brief bursts of training activity. Also, only use reward-based methods which major on encouraging the dog to behave, and be prepared to have the patience of a saint. That said, when all the stars align you will have a happy, well-trained, and obedient dog that will give you an immense sense of satisfaction at what you have achieved.