First of all thanks for the advises! Vibrations was just what the lock needed. Here is the way I did:
1. Removed the trim list around the tumble.
2. With the key inserted (the one without plastic on it) I used a electric jigsaw, which makes some good vibes, and put the plastic handle of the saw against the key itself. This made it possible to turn the key with a small wrench. No violence applied!
3. Made a 2mm vire with ends cut diagonally and inserted it into the slots for about 2,5 inch. I found a great website for the w201 where this tool were described very detailed. Big thank you to the owner of this site.
http://www.geocities.com/shvoldum
But here does the story end...I hear the klick as the vire goes in but the tumble is still stuck. I am working with the car at the moment but can get the tumble out. Am I missing something???
I also ordered a new tumble with keys(on my VIN#, of course) from my nearest dealer and he said it will cost me about 40 USD.