Some time ago I read a book about a man who has to help hell to reverse the apocalypse.
Heaven started the apocalypse because the rate of people going to hell is growing by the years. Hell chooses the Protagonist and a devil (or was it called demon?) to travel through time and speak to great philosophers to find the meaning of life, which is needed to reverse the apocalypse. For the time-travelling part they had the cellphone of one of the archangels.
I can remember one scene in particular: At the beginning of the book (when the world still exists) the protagonist is happy because he just received his philosopher's degree. Someone steals his degree (the certificate) and while chasing this Person he runs into a church where he accidentally soaks himself with holy water just when the world ends. Last Judgement is passed onto the humans by machines (for budget reasons or something like that) and the protagonist can't be judged because in the last moment of existence he was soaked in holy water (which would bring him straight to heaven) and cursing (which would bring him straight to hell). It turns out that the Person who stole his degree is the devil/demon who he has to work with, but it dropped his degree to fetch an orange which, as the world was rolled up like a carpet, fell through a hole over Argentina.
Overall the book was a bit crazy. I'm pretty sure that the author is German.
I read the book about five years ago and it was not an old book, released the same year or the year before that.