Put peanut butter in his mouth every time he barks and wait until he is a year old, and have him fixed. The peanut butter will not hurt him. But it will not allow him to bark. And after doing this a few time. He will get sick of the peanut butter and know what is coming if he barks again.
Also just try talking to him. Tell him know, and make sure he understands what that means. And if not try showing him, with rolled up newspaper. Dogs are very smart just like our children. They must know what No means and what going to happen if they do not lesson.
But I think you will find the peanut butter will help and it’s so funny too.