welcome to the forum, Heiko.
And as mentioned before, don't worry about your English.
johnboy:
As far as license plate sizes are concerned, there are few options out there in Germany; most notably the use of license plates for light motorcycles. They fit well, but generally may only be issued by the local DMV for classic cars registered as such and when space permits the use of plates of larger sizes. In marked contrast to early Mustangs, early Cougars have certain advantages at this particular matter. Relevant legislation demands the taillights may not be covered and the function of the license plate illumination must be ensured. Also, since a classic car usually may not be altered in a way that "permanently changes the distinctive appearance of a make and model" (i.e. shortened taillight assemblies). Accordingly, small motorcycle plates can be requested and usually, will be allowed - at extra fees, of course.
Up front, the larger regular plates fit fairly well, although protruding to the left and right. So, up front small motorcycle plates shall not be granted, usually.