This is a quite entertaining read. Günter Wallraff is a kind of "left activist". His  work somewhere undercover and then writes a book about it, mostly during the 70ies. So he once dressed a turkish immigrant in Germany and experienced from the first-person experience how it is like to be a part of this minority and work as a so-called "Gastarbeiter" (that book is called "Ganz Unten".
This time, he worked as a journalist at the "Bild-Zeitung", the prominent german yellow press paper.