Very well!
This will be a long post...
You all know what dinosaurs were, right?
Well according to some paletheolongists, one kind of dinosaurs by mutation(you'll learn in school that mutation is extremly important for evolution) learned to breathe fire! How is that possible you ask... There are two possible way to do this. For the first one, it's important to know that all organic beings are composed mostly of Hydrogen and carbon, right? Now hydrogen is a gas that burns with high temperature! So if dragons had ensims which would take hydrogen from food, they would be able to store it and use it to breathe fire, aswell to fly!
Another one, comes from today's animal world. There's a bug called the bomber bee which, by combining two liquids, creates liquid with over 2000°C in matter of seconds! So it is possible that dragons had the same ability to create two chemicals in their glans to produce fire!
But WHY do I believe they were real? Did you know that even ancient egyptians drew and wrote about dragons? so did 3000 years old chinese and japanese civilisations!
Tell me, is it possible that civilisations that lived in Europe, africa, Asia and America (ancient Maya and Inka did the same thing) believed and made up the same creature without it acctually existed! I don't think so! Keep in mind that thay had no comunication what-so-ever, so they couldn't have just replicate believes of one nation!
Which means they must have existed!
Do i believe they still exist?
Yes, but not the way you imagine tham! When the great catastrophy(giant meteorite that hit the Earth) destroyed dinosaurs, one kind survived to this day, buy going to the sea: Crocodiles! In my opinion, so did dragons! after that some dragons returned to the surface and remained there, until humans killed then all(in middle ages there were big expeditions to kill dragons,there were tools to catch them, even a science that studied them). But I think that sea dragons remained there hidden from sight, yet to be discovered! Keep in mind that only about 30% of Earth's sea has been uncovered!
Watch documentary "Dragons world a fantasy made real". it is al fantasy made, so dragons in it aren't real! Basically it filmed in what if way, but it explains A LOT!
Hope I explained everything, and haven't forgot about something...