I assume the question involves how, in the case at hand, a Polish person with moderate proficiency in English can avoid impolite expressions while speaking with a "native" English speaker from the UK, Canada, the USA, Australia or New Zealand. Correct?
That's a difficult question as I assume the real risk is avoiding the traps associated with unique or unusual local meanings attached to words or expressions. In the case of English there is a great deal of variety in this area from Britain to Scotland, and in the USA & Canada from region to region. Australia is an entirely different challenge. Americans are generally more direct in their speech than the British, perhaps in the same way you referred to Poles.