Time is a dimension, but not like space

Thee is no „Stillstand“, you can’t stand still relative to anything in the universe.

Hm. That’s a possibility. As I understand it though, an infinitely massive object would not move in space, and would experience time at the absolute rate of one second per second.

Although that sounds theoretically impossible, I would remind you that somehow the opposite seems to be possible (a particle with zero mass that moves through time at a rate of zero seconds per second), despite that not making a lot of sense to a layperson.

Footnote: Talking about time in seconds makes very little sense here because our notion of time is so heavily linked to how light moves through space, but hopefully my point is clear. Maybe someone has a better unit we could use to measure time independently of space?

Your point is clear. As far as can wrap my head around those theoretical concepts: An infinitely heavy object can’t move in space because there isn’t any space left to move. I would say that this object would have concentrated all mass in one point, no space left to move. No observer left to measure. I would also say that there can’t be two or more infinite masses at the same time, or they would move (at the speed of c (?) But that would have additional implications on mass and time) to the point between them.

But back to observable reality: let’s say you fall into a dark place where the time stands still and that means you are not moving, from an outside observer you are still moving relative to the space outside your black hole. Let’s say the observer fall on his way to your black hole into another black hole and experience the same phenomenon like you, from a third observers perspective everyone is moving.