Where is the best place to rent a car in Germany?

I'm going to travel around Germany for a couple of weeks - I want to not depend on train schedules. I'm thinking of renting a car, but I'm not particularly familiar with the services there. Who has tried what, are there any convenient options right from the airport?

I was also faced with the choice of where to get a car in Germany - not always convenient through the big rentals companies. I was looking for something simpler and cheaper, especially with the possibility to choose a car closer to the desired neighborhood. I came across a platform where car rental in Germany is presented in one place - you can check out the options at https://getrentacar.com/en-US/germany

Thank a lot!