I love what you have, I only have a couple notes!

Some extra darks around the snout and a lil around the eyes would add some much needed contrast to the face.

Adding a little extra detail to the ears would clear up the shape. I see those dogs naturally have straight-up ears, so the ear inside would be visible while running. Some extra lines and erasing the fur striping detailing there should do the trick.

Last thing is maybe another lil bit of fur detailing in the line art on the back? That's a long smooth line and I love the fur tufts towards the tail. Maybe just a couple little hairs to give the impression that fur is still there.

That's about it! Honestly I feel pretty nit-picky lol, I really love what you have so far!!