give me three examples of how David was a really nice person in this story an how he changed through the story

I think David is a pretty static character. He is kind and generous for the whole book. Davis certainly learns about people and the world, but his fundamental character remains the same. David does various good deeds throughout the novel:

-He saves a girl, Maria, who is trapped in a burning barn.

-Lets Sophie paint his picture.

-Carries gas for American tourists.