You need to start from the ground up. Start with gaining respect with showmanship work. Good ground work is going to be the foundation you need in re-training your new horse. Get him leading, and lunging properly and to both sides. Get him pivoting (on the front and hind - this is an in hand exercise) and side passing/leg yielding from the ground!
You can do most of this with the horse bitted, but concentrate on working on all these things with aids on his girth and barrel area, try not to work on his face. Work "on" his body - with you on the ground.
Then when you start riding, work on perfecting everything at the walk. Once you can turn all directions, back, circle, work laterally etc at the walk with YOUR body aids, you are ready to start working at the trot.
Try not to work "on" his face, while you are riding. You never want a horse to get used to you riding his face.
What kind of bit are you using and how does he respond to it?