There is no cure and no exercises can cure this speech disorder. Stammering can't be controlled because stammering starts in your brain, not your mouth/throat/tongue. You can completely change the way you talk, sound like a robot or like you're short on breath on every word, but is that really that much better than just stuttering? I just say this because ive seen countless people really try these breathing and shaping and speech manipulation techniques and then they dont work. And get told the techniques work, so the problem must implicitly be themselves. And that's not true.