Considering how difficult it is to verify information +200 years old and how likely it is that theories based on some information would fall apart if one piece

Considering how difficult it is to verify information +200 years old and how likely it is that theories based on some information would fall apart if one piece turns out to be a fake or a lie, I wonder how much we actually know about history, or more like, what's the amount of lies we believe and live by everyday thinking it's undeniable truth because a group of "experts" thought it is.