Hi Nita, welcome to YT. Max is adorable.
I have a Biewer too.
When I took him to his first visit with my vet they heard a murmur (Grade 1 out of 6, 1 being mild). Like your vet, at that point, they weren’t that concerned. Apparently, it is not all that uncommon in young puppies and often they do grow out of them. I think it is by around six months of age.
At Gus' next vet visit, a few weeks later, they could not detect the murmur. He is now two years old and I have had all three of his vets listen very carefully (overprotective owner but they are great about it) every time I've brought him in. They assure me his heart is healthy.
Since it sounds like your vet's response was a lot like my vet's it could turn out to be nothing or a mild murmur that he could live with to old age.
I do not know if he is suitable for breeding even if he does grow out of it. Hopefully, someone else can give you some insight on that.
Best of luck.