Complex sentence: Mr. Rogers walks in the Post Office and leaves his wallet on the desk, the postmistress walks out with him, he gets her to give him the key and he runs back to the Post Office to steal the petition about the road.
Split into simpler sentences: Mr. Rogers walks in the Post Office and leaves his wallet on the desk. The postmistress walks out with him, but he gets her to give him the key and runs back to the Post Office to steal the petition about the road.