No one knows anything for certain. Our beliefs about reality can only be based on what we experience, and what others tell us they have experienced.
Basing your knowledge on evidence is known as science. Our brains have evolved to function based on what we and our ancestors have experienced. Everyone is a scientist.

"Life is pretty simple: You do some stuff. Most fails. Some works. You do more of what works." - Leonardo da Vinci

"The whole of science is nothing more than a refinement of everyday thinking." - Albert Einstein

"It may be that the race is not always to the swift, nor the battle to the strong, but that is the way to bet." - Damon Runyon

Within a few years of birth we realise that not everybody knows everything (Theory of Mind). Most people soon realise that nobody knows everything. Eventually a few of us realise that nobody knows anything.

"Nothing is real." - Niels Bohr

"Real knowledge is to know the extent of one's ignorance."- Confucius