It's may or may not be fact

According to time if you change anything in the past it will make changes in your life and everyone's life. Then you can't build a time machine because you changed the past which made you to build a time machine, so we should not and can't change anything in the past.

It's just like grandfather paradox...

          One day a boy thought that his grandfather is giving more work to him or something which made him stressed andso he build a time machine when he grows up and goes with a gun to the past when his grandfather was born.He kills his grandpa who is a baby that time but it's a paradox.

 He don't knoe that when his grandfather is not there, How would his father would have born ? How he would have born without his father? How would he built a time machine with no reason?

So, everything comes back to normal. His grandfather is back.

So remember you can see the past but can't change the past. Believe that present is in your hand.

But you can see the future see the past but you shouldn't change anything thats matters.