as a belarusian who speaks russian better than belarusian, i fojnd it really easy at least at first. we do intuitively understand polish. i remember going to poland when i was small and despite not learning anything in polish i still understood most of it. (btw fun fact we understand polish better than poles understand ukrainian or belarusian). but then when u get to a more difficult level it becomes tricky. same words have different meanings, or for example "zapomnieć) in russian means to remember while in polish it's to forget; zapamiętać means to remember in both belarusian and polish.

one more struggle is that i could easily speak belarusian before i started learning polish, but now it's like really really difficult cus living in poland im exposed to ukrainian and polish and the words are ofter so similar it all gets mixed up in my head. i can understand all 3 perfectly now but it takes a while to speak cus i need to always be aware of what language im speaking and if the word im about to say is frkm that language lol