Go to a museum, a bit one like the Smithsonian or something. You can see the dinosaur bones for yourself. Or you can go to a public dig site and dig some up yourself.
Dinosaurs were real. theres no question about that.
For "Aliens", if you listen to the rules of mathematics and probability, there are other beings out there that are as intelligent, if not more, than us.
Now, if they have come to earth, thats a completely different type of argument.
As for the rest, they exist in our imagination, but I don't think so in the real world






