Azzam
There is no problem if how reality can be known is sorted out from all that which cannot be known. That being a function of existential considerations not practical problems associated with sensing. That is how does reality occur, for us. Otherwise there is this indeterminable foray into metaphysical presumptions. Although most of the time people do not realise this because the maths, or whatever model, disguises it and gives the analysis a superficial gloss of objectivity. Using your words, we only have the "material world" and "knowledge of reality".
We are not "restricted by matter", we are matter. Indeed there is only matter (or to be more precise, if matter is a technical word referring to one type-stuff-physically existent stuff). It is not our consciousness, it is sensory detection, which is a function that has evolved across all organisms and utilises certain physically existent phenomena, which occurred before the evolution of sensory detection systems. Put simply, there is 'something out there', an interaction with another 'something out there' creates 'something else out there' and sometimes a sensory organ is in its line of travel and hence receives it. Otherwise it hits something else, like a hill, the moon, whatever, and ceases to exist.
Neither space nor time are created, they do not physically exist. 'Stuff' exists, and what is the difference between different examples of stuff, as defined by us, by virtue of our evolved system of sensory awareness, is designated as space. In reality it is just other stuff. In other words, albeit for understandable reasons, we are conceptualising the constitution of reality, incorrectly. There is alteration in the configuration of this stuff. That happens at a rate when compared to other changes. Timing measures this. Put simply: there is stuff and alteration thereto.
Nothing is separating you from the future, there is no such thing as the future. There is only a present, ie when stuff is physically existent in a particular state. Alteration then occurs and it is in another physically existent state, and so on. Albeit from our perspective, there are vast similarities, so we think much still exists in the same state, and therefore get confused as to what constitutes present and past. The 'future' is a present that has not occurred, ie it does not exist. We can make predictions as to what might occur. We can take action which affects events. But the latter is not 'altering the future', it is causing a different present to occur from that which would otherwise have done so.
Apart from the fact that spacetime misrepresents spatial dimension, it 'double counts' time. Because it has reified this characteristic into reality, so there is deemed to be change within reality, which there cannot be. Then it times it (as in timing). There is only the measuring system-timing. We can establish what occurred (the present) as at any particular point in time, or we can compare the rate at which changes occur.
The relativity theory of Einstein (or really Lorentz) before it got subverted by incorrect conceptualisations of time and space, was that matter actually altered in shape (ie in the line of motion) when a differential in force (eg gravity) was incurred. Which also caused a changing rate of momentum. This may or may not be correct.
Paul