For the OP:
Maybe ask your parents/grandparents if they have ever lived? And maybe they even remember their own grandparents who lived before them? Etc. That is history, it's not only the major events, but also everyday life. Yesterday is also history.
Also think about why is your country called Poland and how was it formed? Out of nowhere? By aliens? Or was there maybe long series of historical events that led to the current state of the Polish nation? Maybe you can even see some old buildings around you to remind you that there have been life before you.
Of course no one can be 100% sure what happened in the past and it is well know that historyy is often written by the winners. But the historians (at least the professional ones) try take that to account in their studies and use some logic and trustworthy evidence.
But if your problem is that you're not sure if the world is only your dream/imagination/mushroom hallucination/Matrix I suggest you to just ignore that and continue living as you have been, there's nothing you can do about it (unless you take the red pill).
Sorry if someone has written something like this before, didnt read the whole thread now
E: Stupid lagging forum made me lose my message twice