Did the Big Bang happen?

[Deesse23]

So here's something about the big bang which never made sense to me. So as far as I know a simple explanation of what the BB is would be this, we can observe that the universe is constantly expanding, therefore we can assume that if we go backwards in time then the universe is always shrinking. Feel free to correct me if I'm wrong on that point, but that seems to me to be a simple summary of the BB theory.

If that's the case then how is it that, if we reverse time, the sun and earth gradually get closer to each other?

If the universe is shrinking then so is the distance between all planets as well, as the stars which they orbit, so wouldn't this mean that earth would be consumed by our massive sun?

The expansion rate of the universe is known. Take it and calculate for yourself by how much in the past the Sun and Earth could have been closer (leaving all other things like gravity out!). Its really no rocket science.
By how much do you think the distance between Sun and Earth would reduce if we turn back the clock to the formation of earth some 4bny ago?