How Old is our Universe?

Twitty You ask what is a universe? Its definition goes like this(my
view of it). It is a place where all existing stuff aggregates. The
whole of all that is created. It embraces all celestial bodies and all
of spacetime and its other three dimensions. It is housed inside the
cosmos. It is organic with intelligent life forms such as us. bert

There can be no such thing as multiple universes though.

Because if there is, then this not not actually the universe, just a
little bubble inside of the universe.