Frieza might initially be shocked. He's used to being a feared and powerful being, and the idea of having a family is very foreign to him. So he could be in denial at first.
For Yamcha, you can focus on his growth from being a bit of a comical character to a more serious and respected fighter in the context of his relationship with Frieza. Maybe he learns from Frieza's cold and calculating nature how to better strategize in battles. For Frieza, his development could be about him learning to care for someone other than himself. He could start to see Yamcha as an equal, which is a huge shift from his usual superiority complex.
Black holes were formed by the collapse of massive stars. When a star's mass was large enough, it would experience a supernova explosion, releasing extremely powerful energy and matter. During this process, the core of the star would be squeezed to the limit, forming a black hole. The formation of a black hole is proportional to the mass of a star. As for the specific information on how the black hole in the sea was formed, there was no relevant answer in the search results provided.
Hei Longtian's original form was one of the five great divine dragons of the ancient god clan. He was the representative of the most primitive and ancient bloodline of the entire god clan.