What Was There Before The Big Bang?

This week, our daughter sent me down a rabbit hole. In one of her books, we learned about the Big Bang. As we were reading, she asked: «Were you still a baby when that happened? Or were you not even born yet?» First: Thanks for calling me old, I guess? But then, how do you explain that there was a time when not just nobody, but nothing existed, not even time? My head starts spinning the moment I start thinking about it, and searching for answers on the web didn’t stop the spinning, it just gets more confusing the more you learn. If you know of any good explainers that work for a 5-year-old (and her dad who is roughly as old as the universe), please send them my way.