Is anybody here knows on what is the very first religion?

i don't know who's first but what i know is that jesus christ had started the christianity

True, religion is man-made. Look at the Christian churches these days. There's so many sects and whatnot, it's hard to keep track. Now, for your answer, if you read the bible, Cain and Able offered sacrafices to G-d. Sacrafices were continued throughout the generations. Even Noah knew which animals to sacrafice as well as eat long before it was written law. Abraham was asked to sacrafice his only son, Isaac. So, with this, I would definately say that Judiasm is the very first "religion". Being a Jew is also a way of life.