Oh dear I am sorry to read this Celin. I would encourage you to do some 1-1 sessions with a trainer, but continue with obedience classes. Maybe up the training sessions a bit, things that calm him down and make him use his brain, like hiding things and he has to search for them, in the house and in the garden. You could also do laying a trail for him, which he follows to find a treat. I use frankfurter sausages for this, the ones that come in a jar with smelly water! I use a syringe to suck up some of the liquid, and lay a trail with a bit of sausage at the end as the reward. It takes a bit of getting used to, but dogs that like to use their noses really seem to enjoy it once they get the hang of it.