Sorry to hear of your problems. When you say Neiman do you mean the factory fitted steering lock? (MM 667-840)
If so.....
You would need to remove the escutcheons, slack all the mounting screws and drop the column as far as possible, then start drilling or grinding either the screws or the aluminium. You may be lucky and find that the security screws that hold the thing in place can be punched round or better still were not 'sheared' on installation, leaving the hexagon head ready for your spanner (wrench).
You can get the entire upper column out of the car and work at it on a bench, but that takes time and will be required if you have a genuine Neiman lock that clamps to the column on one side as a ring rather than a U, as it has to be slid off the outer column shroud lower end.
Once free you will be able to drive the car and then need to get a replacement steering lock and switch assy, if you want to return it to orig. I do not know of any one who supplies the lock barrel and keys alone.
If the wheels are straight ahead and the place you want to park it eventually is directly in line you can remove the switch wiring from the back of the lock assy and start/stop the car by shorting things out (hot wire). Remember it will not steer tho and if you get it wrong may melt the wiring harness!