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?

>>1
if you believe in Tegmark 4, there is no distinction between "mathematical construct" and "real thing"