Upvote:7
You have to officially depart Germany before midnight on the day your visa expires. After you cross the line at passport control you are no longer "in" Germany as far as immigration is concerned.
However, unless your departure flight is shortly after midnight you won't get past security. The cutoff time is dependent on the airport but "8am the next day" will definitely be out of the question.
You need to either get a flight before your visa expires or talk to immigration about it. Preferably well before midnight on day 3.