Having spoken to you last night I was kept wondering why you have the desire to get on a public road and see how fast you can go. The majority of the 2 lane unrestricted autobahns tend to be quite congested. The 3 lane roads (correct me if I’m now wrong) are all subject to the blanket 130kph top speed. Also, German cops are always on the lookout for irresponsible use of the roads, it’s not a simple case of turn up and rag it.
Have you considered attending a top speed meeting, have a look for Straightliners, mostly held at Elvington Yorkshire, but maybe there are now events held again at RAF Woodbridge not too far from you. I’ve not attended any for 10 years since I retired from racing.
As a long time land speed racer myself I’d consider this to be the safest way to enjoy high speeds. Like any form of motorsport it’s not free of danger, however it’s possible to have high speed incidents without the likelihood of getting rearranged by the arse end of a 40 tonne truck. I crashed at Woodbridge 2009 at 192mph according to the timing lights I demolished - I walked to the ambulance practically unscathed, the bike was totally totalled completely, 2 weeks before a road trip to Spain. Oops, better buy another quickly.