I just went over this in school. He didn't reform it, in fact he joined it, he was originally a lonely soldier and later on, he gave his input about ideas and stuff and they agreed so they decided to make him official leader of the nazi's.
Do you know what reforming is? To bring changes to. Yes, he joined the Nationalist Socialist People's Party, and he rose quickly in their ranks because he had solutions for the shitstorm Germany was in. Once he got power in the Nazi Party, he did reform it. He was never a "lonely soldier" he won medals for bravery. The Nazi Party was basically the German Fascist party.