They forcefully mutilated English and created this "monster" of theirs just for the sake of it being different. I hate those "Z"'s
Ah, yes, those Americans created this monster with the z's. Since you are self-taught, try reading the Oxford English Dictionary:
"In fact, the '-ize' forms have been in use in English spelling since the 15th century: they didn't originate in American use, even though they are now standard in US English. The first example for the verb organize in the Oxford English Dictionary is from around 1425, ...
The OED's earliest example for realize dates from 1611...
The first recorded use of the verb with an '-ise' spelling in the OED is not until 1755 - over a century later!"
blog.oxforddictionaries.com/2011/03/ize-or-ise/
As originally published, Shakespeare wrote, " 'Loves Labors Lost', not 'Loves Labours Lost'." (Although it was changed by some later to add the French spelling with "our".) However, try doing a search of Oxford University Press's 1915 "The Complete Works of William Shakespeare" for how often the Bard wrote "I learnt" (and not "I have learnt") vs "I learned" or the shortened "I learn'd" and tell us again how the the Americans changed the language:
oll.libertyfund.org/titles/1612
If British English is more popular in Poland, it is likely because many Poles want to work in the U.K. British English has evolved more than American English. That makes it more complex, but not more authentic. (It is good to know phrasal verbs, but better for clarity to avoid them.) Some Poles may prefer what is more complex, and Poland has been flooded with British English teachers, but few modern Brits were taught basic grammar in schools. Very few recognize the ellipsis in their speech, and are thus ignorant of linguistic structure. To learn proper formal English for communication, a discriminating student would do well to find an older American or South African who know those rules rather than insisting "We talk like that", even if they shouldn't.