Endgame spoilers

After watching endgame I realized something there's two concerns. 1st one being how is ||present Nebula still alive after killing her past self.|| 2nd one being there's now a paradox in the mcu. ||When thanos traveled forward in time he got dusted/killed. Which means his future self never snapped his fingers, but that would mean everyone is still alive. However if he never snapped his fingers they never went back in time to bring him in the future. (And the process repeats)||