Was there space before big bang? Or who knows there might be different heavenly bodies that we might not perceive?
The answer to this questions turns out to be a "yes". The big bang is a sudden rapid expansion of space, so yes, there was space before the big bang. To understand more, check this vulgarization video by MinutePhysics who corrects some misconceptions about the BB, since you seem to not know the Friedmann-Walker-Robertson-Lemaître metric.