How do you know you are exist?

How do I know I am real? It's an obvious question until I try to answer it. René Descartes in his book tries to answer the question. All his knowledge came from his perceptions of the world. Same as me. I know that I'm watching the screen with my eyes and hearing the music in the background with my ears. My senses show the world as it is. But sometimes my senses deceive me. For example, sometimes I mistake a person far away for someone else. But now, I know what is right in front of me is real. My eyes, my hands, my body. Only crazy people deny that. Anyone who'd doubt that must be dreaming. But what if I am dreaming? Dreams feel real. I can believe that I'm flying, or fighting with monsters when my real body is lying in bed. Maybe my body isn't really here. Maybe all of reality, like time, shapes, colours, and numbers, is false. Maybe an evil demon is deceiving me and tricking me into believing reality is real.
If I am persuaded, it's good, because by being persuaded I would prove that I am a persuaded being. I can't be nothing if I think I'm something, even if I think that something is nothing, because no matter what I think, I am a thinking thing, or as Descartes said it, 'I think, therefore I am.". The truth is, we may never be certain of anything.

Szia Viktória! Jól írsz angolul. :)