How deep can I lower my MX5?

I had a dream last year and bought a MX5 NB. I would like to put a lot of money and work into the car. I would like to buy a chassis for the car next, because it is still way too high for me. What would be the minimum height here in Germany or Schleswig-Holstein. It should be as low as possible, however, so that the TÜV takes it off. I added another picture. That would be the height I would like to have for the car.