Car-sharing or Uber in Germany/Austria

Trains in Germany: Deutsche Bahn, Flixtrain and various smaller ones, mostly regional, e. g. ODEG.

Public transport in and around Frankfurt: RMV.

Public transport in and around Berlin: BVG and S-Bahn Berlin. They co-operate as one common network with one tariff system. There is also Jelbi app for Berlin including sharing services but I do not know if non-residentials can use it. Always time stamp paper tickets before the journey / day (see ticket machine).

For driving a car in Germany be aware that you need a valid driving permission - your national driver's license may not be sufficient. Can be very expensive when checked or without insurance coverage in case of accident.

In Germany just take a taxi: metered rides, educated and licensed drivers, safe and shortest ways for customers.

Stay away from Uber or Freenow app in Berlin!
There is no classical Uber in Germany - only calling a rental car with driver. Be aware that these people are not professionals compared to taxi drivers and partly acting illegal; fully known and covered by Uber and others. Berlin authorities counted recently over 2,000 illegally operated rental cars with drivers (no concession). As customer in case of accident you may end up without insurance coverage. Sharing industry by US companies means in most cases privatized profits and socialized losses.

In the past year I've used SIXT, Enterprise, and Hertz car rentals, but never car sharing. It's not hard to get around using the trains, buses, and subway or regional trains inside the cities. And most smaller towns also have rail and buses. But if you get stranded you'll need to use the local taxi service.

Sixt is a car rental company not a car sharing service. You will not find car sharing services in rural areas of Austria nor will you find Uber.

That location in Carinthia is best reached by renting a car.