They are in Egypt, and this person is Moses. He sees a bush full of flames, from which God is calling him, Moses, I am the god of your father, of Abraham, of Isac, and the god of Jacob. The Lord says I have seen the suffering of my people, He says to Moses I will send you to Pharoah to bring my people out of Egypt.
As from how tough Phorah was being, God sent Moses to strike the water of the nile river turnng it to blood
7 days later, after God ordered Moses to strike the river of nile, he sent him to ask again to set his people free, Pharoah still said no, so Moses stretched out his hand and frogs, came from all of the rivers.