hey - you were going to be by my side forever, you were never going to let go of my hand, you were going to stay by my side forever, you left me now you'll stay alone.
Remarks about the translation
The word "hani" which is repeated several times, has the meaning of "what happened to", but it would be unwieldy to keep repeating that here.
Hej! Miałeś(-aś) być przy mnie na zawsze, nigdy nie opuszczać mojej ręki, miałeś(aś) zostać przy mnie na zawsze. Porzuciłeś(aś) mnie, więc zostań w samotności.