What came before our Universe?
We don't know !
Space-time came into being after the Big Bang,
This was triggered by a perturbation in the quantum foam, which led to an unraveling of symmetries, giving the Universe the shape and character it now has.
Before the Big Bang space-time was a singularity, and the critical point was the Planck Time,
A singularity is an abstract concept and represents an indeterminate state of the Universe.