who actually was the german teacher ? what did the "good luck for tomoroow " signify the day before the examination ?

give new answer in 2-3 marks in easy simple language 

Hi :)
The German teacher was a friend of Evans', a member from the technical institute. Since the 'teacher' was aware of Evan's plan to escape, he wished him luck. To other witnesses, this would be interpreted in terms of the German exam to be held next morning.