The minimum age for car rental in Germany is generally 18, although that can vary depending on what vehicle category you want to book. There is an underage driver charge for those under 23 years old.
Avoid any hassle if your plans might change by choosing to pay later when booking. Then you have the option to cancel your rental before pick up free of charge.
You can rent a car with a debit card in Germany if it’s connected to a major credit card company like Visa or Mastercard. Maestro cards are also accepted for most car categories.