Hi again.

I am not expert on german law however a quick check of one of underwriters jguides shows the following exclusion:

(The Insurance does not cover the insured vehicle being used on the Nurburging Nordschleife or on any form of motorsport circuit or for any off-road activity.

I guess it is up to you if you drive the 'ring without taking out seperate cover,I wouldn't advise it though.