I'm sure you can tell this is over-exposed, the dog disappears into white...the horizon is lower on the left.... Composition isn't the worst...but it could improve a little...apparently what we do with composition is use it to tell a story of sorts...this is pretty good...I could see this with the dog chasing after the bike...both in crisp focus while in motion...slow shutter speed while panning with the subject/s....keep shooting...more will be along to explain further the few things I've noticed...