It's done!

[kelii]

Now, please tell me how to improve

[Artfix]

Is this an oil painting? Colored pencils? I think its wonderful!

[kelii]

Thank you It's watercolor and colored pencil.

[Black Spot]

I like it too. The only thing that slightly bothers me is the lower jaw. Wouldn't the jowl partially cover it. I take it it's a bull mastiff?

[kelii]

I'm not sure about the lower jaw. This the photo I used for the reference.

[RangerX]

I'm not sure about the lower jaw. This the photo I used for the reference.

i see it just before the nose its flat no contour adjust the values, also the upper lip under the nose can be lowered

[Black Spot]

I think it needs more shadow as it does stand out a fair bit. It's nowhere near as bright in your ref even allowing for the cast shadow removed.

[Chris Sanders]

i like the rim lighting in the photo. maybe darken the dog and punch up a rim light. might add more interest. also the collar looks awkward in the painting. it would also look better if it followed the contour like in the photo.