i cant speak for polish, but in dutch this sentence would be "verveel je je?". if one were to leave out the last "je" ("się" in polish), the sentence would be incomplete. i guess the same applies to polish
Im polish and Nudzisz would mean Bored but you cant say Ja się nudzisz because nudzisz is for ,,you,, as in are you bored ( czy ty się nudzisz ) and you would have to add czy ty and się because czy = are/is ty= you się= im sorry but i cant explain it