i don`t know Polish language but as a Serbian i can say that i quite nice understand Polish. i understand Polish well when listen and when read. i am sometimes slow to understand full sense (eventually some particular word) but, in general i always understand meaning of talk/text.
let me show you something...POLISH METAMORPHOSIS OF TWO SERBIAN FOLK POEMS
Some significant similarities between Polish folk poems: Ach, ptasku w lasku, wsystko stanowis..., Ty ptaszku w lasku, wszystkich rozweselasz... and A ty, ptasku, w lasku, co wsystkich spokoisz... from Kolberg's collection Mazowsze (VI, 533-534; VII, 1593) and Serbian folk lyric poems Tri najveće tuge (Vuk, I, 542) and Kletve djevojaèke (Vuk, I, 368) encouraged the authors to focus their research to possible intertextual connections between Serbian and Polish poems.Polish:
O matko, matko! Bodajś nie pożyła,
żeś nas obojga ze światu zgładziła.
(Približno: O majko, majko! Dabogda ne poživela,
zato što si nas oboje na onaj svet oterala).
When you have such a similarity, practicality overlapping in epic poetry you know that analyzed ethoses were one and same ethos in past. We know Slavic, Polish and Serbian history, we know that we are separated (territorially) by hostile foreign force.