This contains serious mejor spoiler.Well I have some thoughts about the ending i think jonas and martha are like the observer in Schrödinger thought experiment 'as you observe, the wave function collapses into a definite state' And I think we ,the viewers are like the observer too. As we see the cars turning back and marek goes back to his father our wave function collapsed and thus changed into a definite state ,A reality where tannhaus's family did not die. So for us the viewers jonas and Martha can not exist and all the characters who were created by bootstrap paradox.