This instruction will show you guide on how to remove the front bumper on Mercedes W212 2009-2013.
Here is similar topic about bumper removing for further reference:
Unlock the two clips
Remove the two bolts with the sprocket key
Disconnect two hoses
Unscrew the bolt in the middle
There are also two bolts on the left and right side, remove these bolts
Pull the bumper slightly forward and remove the two bolts from below on both sides
Disconnect the two fog lamp connectors
Also remove the parking sensors connector
Removing is finished
More cases about Benz W212, please refer to BENZ E-CLASS W212.