They say you cant go to the past and alter the future because the past becomes your new future and your former present becomes the past which now cant be changed by your new future. Someone please explain this to me. Does it make sense?
Well... no. ;) I may not have payed a lot of attention to the movie when they talked about that, but no. Time travel in movies rarely makes sense (except maybe in Back to the Future) but Marvel's rules are generally nuts. I try not to take it too seriously.
But, maybe I'm wrong! :D Perhaps some bright person can make sense of the whole thing. ;) Good luck!
It seems like they went into the past and returned to a present that was changed by their actions in the past, i.e reappearance of all those who perished in infinity war. It just seems like it was the same logic as back to the future which they dissed but they also added some new stuff to it like the timeline would get ruined (Tilda and Hulk scene) unless they put the stones back. Not nitpicking just trying to understand their theory... :S