The time paradox - What if you go back in time and kill your parents?

Time is a strange thing.

Just imagine, you go back in time and kill your parents. So you would have never been born. But if you're not born then how can you grow up enough to go back in time?

Or if you go to your past and kill yourself and never return to the present. What would happen then?
Would you just cease to exist?
These type of situations make me think that time is fixed. I feel like the past, present and future are all pre decided.
What do you guys think?
Comment below!