So, in the opinion of folklorists, the Snake Gorinych is not just a fire-breathing reptile, it is the ruler of the elements of the Avatar from the cartoon of the same name. Therefore, there is no contradiction that it breathes fire, moves underwater, arranges earthquakes and flies in the air. Its multiple nature is emphasized and is the reason for the presence of three (six, twelve and further according to progression) heads. By the way, wings are not needed for flight, they are not mentioned anywhere, and their presence is the assumption of modern artists. As the ruler of the air, the Serpent Gorinich can fly simply because of its status - the air holds it and carries it where it needs to be, movement by some physical processes is not required. So you can consider it something like a balloon.

Also Baba Yaga is not just a witch with cannibal customs, but the gateway to the afterlife world. But about that another time.