Could somebody please explain the difference between zurueckkommen and zurueckkehren?
From the little I know, "zurueckkommen" means to COME back while "zurueckkehren" means to TURN back. I stand to be corrected by a native speaker.
You are close. Kehren can mean 'to turn' and so "Zurückkehren" means 'to reTURN' (ie. come back).
"Er kam zurück" refers to the action of him returning or coming back (what did he do yesterday? - he came back), whereas "He's back" is referring more to location or status.
I wonder if people use always Imperfekt or sometimes use Perfekt if needed. I guess that this is like Past Simple vs Present Perfect in Enlgish or P.Indefinido vs P.Perfecto in Spanish - here I feel like people tend to use Idefinido beacause it is shorter version(?). During 2 months in Canada I cannot remember anyone using PP (that is what I noticed back then). Polish (my native) leanguage do not distinguish those two tenses, so it does not count :D Do people care about using PP/Perfekt in everyday speech?