I've heard in bhagavat gita , that krishna is the primeval , eternal ,unborn and has no death. he is thesource

the bhagvat gita has tried to explain that Krishna is the great god himself and not the avtar of Vishnu .Vishnu and other gods are lower to him.it is said that great god himself come to earth to give the teachings of dharma to Arjuna during the war because the trail of his teaching had been lost .bhagwat gita is the book of that great teaching descendant from Arjuna himself