"...we don't know what space, or time is."

Have you tried looking up definitions of those things?

However, it's demonstrable that spacetime is what exists because events cannot occur that do not involve both space and time. A marble can't roll across a table without taking time. Similarly, over time spatial motion ubiquitously occurs. This is apparent when broader view of a given region is undertaken beyond that locality.

"If we look at the photon in the future, it will be there in the past, before we it even knew we would be looking at it."

It is unavoidable that our feeble senses cause us to have limited perception of events, such as motions of elementary particles, and limitations of our capacity to consider matters deprives us of any expectation of comprehensive understanding.

Humility is the foundation of understanding, scientia.

Thanks!