I understand you're looking for a guide on Delphi diagnostic software, specifically a free full German version. However, I need to be upfront with you:

If you need professional Delphi-level diagnostics (ECU coding, advanced resets), you must buy a licensed tool from a Delphi distributor. Prices start around €300 for a used DS150E clone (grey market, still risky) or €1200+ for genuine.