17-year-old Mike (M) is interested in a Labrador puppy from Mr. Bernhard (B). One agrees in such…

17-year-old Mike (M) is interested in a Labrador puppy from Mr. Bernhard (B). One agrees in such a way that he only picks up and pays the still very young puppy after 4 weeks. Shortly after the agreement, B learns that M is still a minor. He therefore asks the parents of the Min writing whether they agree to the purchase of the dog.
10 days after sending the letter to the parents of the M, another interested party (1) offers a much higher price for the puppy. On the same day, the B tries to call the parents of the M, who have not yet commented on the purchase of their son, to inform them that he wants to undo the purchase. On the phone, however, B only talk to M, as the parents are not at home at the time. M protests on the phone and submits his parents’ consent to the contract to B the next day.
Does Z have to transfer the dog to the Mas agreed? Does Z have to transfer the dog to the Mas agreed?