With 200km, the original key probably is worn too much and isn't engaging the tumbler pins.

Rather than the drastic drill, I'd go to Benz dealer (with owners card VIN# and your drivers license - they require ID) order a new ignition tumbler & keys that you'll get in about 3 days.

Have everyone you know do the ignition key wiggle with the new key for a few minutes. Young children often have more patience and luck. Of course, the reward you offer to the successful "key master" can make for an interesting event.

Bob