Visitor event in a nutshell

It really depends to. Lets say if you make a pocket in time.

A pocket in time is basicly a small universe in which exsists between the past and the present. Which is like saying "It exsists but it only exsists 10 seconds before the current time." So it's like a frozen timeline. Which basicly describes the scenario of "We were already here, but you could not see us." Which also leads me to believe the future was actualy the present, but in a frozen state in which was not inhabitable.

That's not it. Put forself in this case. You go, and proceed to hit a button. That button fills the room with a poison FAST. You travel back in time to prevent yourself from ever pushing that button. The result is that you get to the point where you were about to push it, and you make yourself from pushing it. Now there's two yous, also. What happened?

Well, the MAIN timeline would be the one where you are about to push a button, and SUDDENLY, your future self tells you not to. That future self comes from that pocket timeline, that goes from the moment he would have appeared, but didn't yet, because he's the one going back, to the moment he actually goes back, where the timeline ceases to exist. This fraction from one moment to the other can take a year if it's needed, not like 10 seconds.