They left a lot of things out. Harry never learned how to use spells without saying the spell out loud. Dumbledore never visited Harry's aunt and uncles house. They never talked about Harry being an adult in the wizarding world.
I don't know if they had a time limit on how long the movie could be, but if thats the case they did a good job. This movie was to prepare Harry Potter fans for the Deathly Hollows..