Is spacetime wholly a mathematical construct and not a real thing?

Speaking of what I understood, spacetime is three dimensions of space and one of the time. If we now look at the general relativity, spacetime is generally counted as a 'tissue'. So my question is whether spacetime is real or just a mathematical construct to understand different things. And if that is a mathematical thing, what does that mean with its distortion / bowing?

One dimension of time

It feels pretty clunky, a best current guess at a concept

One dimension of time at each point in 3d space? Or 3 sets of 1D x2 space-time pairs?