German-style compounds don’t really expand into anything sentence-like; the word classes they are constructed from are too limited. A typical example is “tunnel boring machine operator”. You could rewrite it to better English as “operator of a tunnel boring machine”, but even that is far from a sentence.
For that matter, consider Llanfair. Shortening a bit, it’s “Llanfair in whitehazel valley by the rapids”, which is still just a subject begging for a verb (and perhaps an object) to be a full sentence. If it were “Llanfair in whitehazel valley lies by the rapids”, sure - but it is not, and I don’t think that’s by chance. Place names appear to be more liberal in what sort of word classes and structure they allow, though - or perhaps it’s Welsh (or “being constructed by the tourist board”) that’s the difference?
English language placenames often cheat by using hyphens (e.g. Winchester-on-the-Severn, MD; Howey-in-the-Hills, FL).
German compound nouns seem to work by allowing determiners to be incorporated into the main noun. You could have “tunnel boring machine”, “tunnel boring machine operator” or “state tunnel boring machine operator qualification test” as single words, but not “green tunnel boring machine”, unless “green” was an essential element of the machine. On the other hand, you can have “Green Thursday” [Maundy Thursday] and “Red Riding Hood” as one word, because it wouldn’t be the same day or person if you changed the colour. As for place names, a number of languages seem to accept compound names as one word as it is a description of the essential characteristics of the location. For example, Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu means:
“The summit where Tamatea, the man with the big knees, the climber of mountains, the land-swallower who travelled about, played his nose flute to his loved one”
If you change any of those elements (“…played his bagpipes to his loved one”), it may be a different summit.
