Watch the video which has worked for us and Luigi is great now.
Have a slack leash all the time.
Do not look at your dog or pat your dog .
If the video does not work try this - when your dog pulls on the leash kick it very gently but enough to make the dog look at you, and come back to you. When the dog is doing heel, give him treats. Note: make a noise when you kick the dog but make sure you do not use that noise when the dog is good. Later, you will only have to make the noise and the dog will go to heel.