Could someone solve this doubt ?

It's a bit late to ask this now but better late than never.

I'm a bit confused about the Avengers.
In endgame, when they go pick the stones, technically the one in which they'll fight Thanos with a new plan is a new timeline, right!
Because Dr. Strange was taught earlier that doing anything weird with time will result in different branches. And it's true as far as we know.

So when the stones were picked , it should have created a new one where, there are no stones now in this one, this should be a new one with no mass genocide. Am I right to think it this way ??

I was wondering the reason they put back the stones so that this new one has a complete unbroken path. But then what about the original one where Thanos won.
It's all so messed up!!! Yelp...