Question:
Who was the head of Kleinmachnow in May, 2018?

Context:
 Michael Grubert is the head of the government of Kleinmachnow from Jan, 2009 to Dec, 2022. 
 Wolfgang Blasig is the head of the government of Kleinmachnow from Jan, 1994 to Jan, 2009. 
 Klaus Nitzsche is the head of the government of Kleinmachnow from Jan, 1990 to Jan, 1994. 
 Ernst Lemmer is the head of the government of Kleinmachnow from Jan, 1945 to Jan, 1946.

Answer:
Michael Grubert