ترجمه - ترکی-انگلیسی - Gün çoktan döndü buralarda ve ben simsiyah bir...

this is a song by Baris Manco, invoking astronomical imagery as a metaphor for personal change
donence (literally the tropic) refers to solstices or equinoxes. from the text i gather it's the winter solstice since it's a message of hope, and the lowest point having been reached, of things that can only go up.
donence has the same root has donmek: to revolve, to change, so it implies a revolution, a turnaround
nadir is your lowest point after which things can only go up, it is an english word.