Which version do you prefer?
1. Time travelers are somehow insulated from paradoxical changes made in the past.
2. Time travel changes result in a new timeline.
The answer to this is "yes" sort of.
First point, every change, every decision every act creates its own timeline.
Second, the technobabble is "gross macro probabilities cancel out random micro probabilities.
The idea being go back and hunt some dinosaurs, bring the trophies home with you, the most you'll be changing is the chemical composition of a few ounces of oil...
OR., don't worry you'll prevent the human race happening, because you stepped on the one small proto-rodent from which we all developed. There isn't just one. We will still evolve, just from a different rat...
Note that in fiction, you can't go back and save your girlfriend or your parents with the time machine, because you built it after they died. If they don't die, you don't build the time machine....
and, if you don't build the time machine, the most you can do about your parents dying is...grow up and become the Batman......
Want to make a change that starts with a gun design, convince the Crown to fully adopt the Fergeson breechloading flintlock.