Have you spoken to an immigration lawyer? I’d make calls to every one in your city to see who could help.
Start with people here, who then in turn could deal with the authorities in Germany if necessary.
NEXT, if that doesn’t work, turn to wherever the clinic is and see if they have visas of mercy or some such, who knows.
Good luck. Worst case scenario, see if anyone will try what procedure you seek either here or in Mexico. Take all ID and utility bills with address, etc, and lots of cash to Mexico.
Prayers up for your success.
Thank you. Good ideas. Bless you.