Same thing happened to me, i just kept trying and eventually i managed to get it, just try
to take out as many people as possible before m12 gets there. Always think of taking out
the panzershreks as a priority.

ya just kill as many as you can

Well, I just beat the level (not blindfolded, of course:D) so here is what I did. First,
try to stay behind the tanks. When a building on your right is blown
open, you need to run in, and clear it out the first floor. Go upstairs,
and clear out all the rooms. Go outside, and hide behind the tanks. When
the tanks stop the next time you need to kill the Germans on the right,
and left. Follow the tanks until they stop again. Now kill the anti-armor
crew in the street. Follow the tanks. At the first chance you need to
enter a building on you right, and clear out the first floor. Head
upstairs, and clear out the floor. Head upstairs again, and kill the
anti-armor crew. Head downstairs, and search the basement. Clear out the
room, and pick up anything you need. Start going through the underground
tunnel. When you reach the building, you need to clear it out. Head
upstairs, and use the machine gun to kill the anti-armor crews. When the
theater has been destroyed, you need to go downstairs. Now go outside,
and follow the tanks. Now kill the Germans that come out of the sewer
behind you. Enter the sewer. This took me AT LEAST 5 hours. But this actually will only
take 7-15 minutes. Enjoy!!!!