This strict teacher will help you with any questions outside of class. Be careful of his cocky tone, he does know what he's talking about. So just suck it up and ask him questions. It's better to understand the material anyway. Anything that has to with defending yourself against the dark arts or just playing wanting to know about those unforgivable curses, ask Professor Baxon. He's surely to give you an in depth lesson. Be sure not to take it outside of the castle.