Question

what existed before the big bang

Answer 1

Stephen Hawking has said that "Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them."

Answer 2

which are existed before big bang are really not defined
and this was said by Stephen Hawking
and really don't think that I copied from the first answered person I have read this so that's why I had said