What do the phrases flew by and"like one solid wall tell the reader about littlewilly and searchlight

The phrases indicated in the question indicate that little Willy entered the national dogsled race along with his dog searchlight.

Explanation:

Little Willy is hoping to win the race so he can get the money and save his grandfather's farm for his grandfather and himself. His opponent is the stone fox who is undefeated in the race.

The main theme revolves around the idea of Little Willey participation in the race for saving his grandfather's race. The term flew by indicate the kind of speed, with which the searchlight ran during the race. Also the like one solid wall indicate the hinderance created by the stone fox for other participants to win.