Going to a concert there on Monday. Starts at 7:30. I see the Metro stops running at 11:30 . Do you think the concerts end by 11? Will i have to leave the concert early?

You should be alright...but definitely leave by 11:00 ...

If the last metro is 11:30pm, you should leave the concert at 11pm, regardless of the possibility of the concert continuing . Or plan to stay at a nearby hotel and not worry about time

Thats cutting it a little close. Like Jeff said, I would leave regardless at 11 pm (the concert should be over or close to it). You also can park at a metro station (for me it's the Vienna metro station) and then ride in on the metro but then uber back to the station after the concert if you're worried about missing the metro because it will be packed. Uber pool has been pretty inexpensive for me in the past.