According to general relativity, the time order of events is relative depending on your position and velocity. This also seems to break causality in textbook quantum mechanics since local changes can lead to global adjustments (collapse, for one) of the wavefunction.

That’s an intuitive understanding, but it doesn’t account for quantum effects like superposition, and it doesn’t account for relativistic effects either.

Basically the answer has to be something like: in the multiverse of possible arrangements of particles, some of them are in your past, some of them are in your future, and some are in neither, but which depends on the observer, who is inside the universe they are trying to describe, and that creates the illusion of the flow of time.

I don’t totally get it either.

This would imply that time progresses in steps. There is no hint that this is the case.