just a balpark estimate of how much of the worlds "history" is acurate
20xx-present: all or most of it (except in rare cases of deliberate manipulation in dictatorship states) thank the
FSM for the internets over 2 billion posible points of view on an issue (and at least 1% of those is archived somewhere)
2000-~1950: major events are accurate and recorded in newspapers, higher precision information is not available other then through unreliable first hand acounts and (sealed/"lost") paper records stored by goverments and large corporations
~1950-~1700 writen records can be taken as accurate only if they have been coroberated by atleast 1 other independent source from the time, large use of cencorship and obfuscation of information occured. archeological data can be taken as accurate if it has been coroberated by writen records
~1700-~500 period during wich larga amounts of information was actively destroyed and/or rewriten only major events can be taken as accurate, and even then would require coroberation by at least archeological evidence and other independent sources
~500-~1000bc information is more sparse, but of marginaly higher accuracy, large segments are encoded using allegory and myth
~1000bc-XXbc only sparse first hand written accounts, and archeological records exist
thats my general guidline
tl:dr
almost evrything you read in the history books is a lie
alot of things you read in reaserch reports are just guesses (but are usualy still MUCH beter then the actual history books)
an example:
hitler was a man (true)
hitler was insane(or the like) (probably not)
hitler was a charismatic leader (true)
hitler killed 7million jews (true(ish) was probably manipulated in some way)
hitler was the worst war criminal of that era (false, see russia, USA)
hitler could have won WW2/taken over the world/europe/expanded more then he did (extremly unlikley, due to the large scale overexpansion mass similtaneous revolts from every anexed country were likely the instant the war ended, or it would have teken centuries to achive total conquest)