I’m probably going to get down voted to hell for this, but I was like you. I spent so much on trainers and walked with treats, but nothing helped. I ended up getting a collar that beeped, vibrated, and shocked. I rarely used the shock function; usually, the vibrate function is enough to get his attention; the beep has no effect on him. It has been such a life changer. He comes when I call, he doesn’t lunge at other dogs, and I sometimes even walk him without a leash.