timeline (spoilers)

I either missed something either the timeline doesn't make any sense.

So, she kills Sator in the past, during their trip to Vietnam or something? And she sees herself jumping off the boat. So the moment was for sure in the past. And the battle was in the past as well since they were waiting for the signal.

One problem: how did they get to the past?

Second problem: if she killed Sator in the past, how did the protagonist met Sator alive and well AFTER that moment???

Even if all did the same thing and reversed from present to past (Vietnam trip, which was quite a bit back, what about food and everything to make it that way back?) still it wouldn't have made any sense. Specially since Sator would have known the outcome of an event that was happening in the past (and that the world didn't actually end with him ...).