There are companies that have 718's for rent like:
https://www.carvia.de/porsche-boxster-mieten/
Best parts to go for high speed driving:
-A31 from Essen to Emden. Straight road, very good road surface (flat). Only two lanes and can be busy. Best to drive early in the morning. Parallel to the A31, but less relaxed driving, is the A1 from Osnabruck to Oldenburg.
-A24/A19 From Berlin to Rostock. Great, with exception of some speed restricted sections in between.
-A5 from Karlsruhe to Basel. Almost no bends, but busy. Ideal for beginners and on sunday mornings.
-A38 from Gottingen to Leipzig.If the Nurburgring would be reborn as Autobahn, This would be it!
-A3 from Frankfurt to Bonn. Busy in the day, very tempting at night. The whole trajectory is 3 lanes!
-A62 from Landstuhl to Nonnweiler.
-A81 from Weinsberg to Wurzburg. On this one Porsche and AMG do a lot of there high speed testing.
-A92 from Munchen to Deggendorf. Hardcore engine killing trajectory thru a dull landscape.
-A96 fromLandsberg to Bregenz. A few parts non restricted are missing.
-A9 from Nurnberg to Holledau. Drives as an empty airstrip. Very fast and 3 lanes.
Please keep next things in mind,
That the German gouvernment advises a speed of 130 in unrestricted parts, if you drive faster insurance can withdraw in case of an accident.
Most of the people are not driving 200Kmph + and can cut in front of you.
German police is very strict when there are speed restrictions especially at road works.
Make sure you are driving in an unrestricted part (white sign with black stripe).
Flashing your headlights is allowed to warn people.
Drive when the german people are asleep and outside holiday months, this will reduce traffic and people that are not used to driving autobahn
