Спопеляєш means "you incinerate" or "you turn to ashes." It's a very strong and evocative verb that you don't often hear in everyday conversation or even many songs.
In this song, the artist uses it metaphorically to describe the intense emotional pain caused by a lover's betrayal. He sings, "А на справді, просто моє серце спопеляєш" (But in reality, you simply incinerate my heart), conveying a feeling of complete destruction and devastation rather than just heartbreak.
This song is about watching someone you love marry someone else. She's in a white dress, dancing her wedding waltz, and she's crying while she dances, because she still feels something for the person telling this story.
The singer keeps replaying the same moment: her white dress, her tears, his broken heart. He asks whether it's better to just forget everything, but the memory keeps coming back anyway, like a wound that never fully heals.
By the end he tries to let her go and be happy for her, even calling himself a lonely bird now that she's gone. The pain of losing her stays right next to the hope that she'll be happy in her new life.