But I have a deadly hatred of sch generally for a clumsy and newfangled corruption—it is either the older sc-, or it is the High Dutch way of pronouncing s followed by a consonant, … The Nether Dutch of Germany hasn't got it at all except as the representative of sc-, and that of Holland has kept the old pronunciation of sk, even though written sch, except as a termination, when I believe it is pronounced s. … and if the Germans, or rather Nether Dutchmen, of Sleswick have to become Danes in the long run, and to learn Danish at school, …
Source: wiktionary
The truth is that the Nether-Dutch of the European mainland and the Nether-Dutch—that is, the English—of Britain and America have long ceased to be mutually intelligible, but that they can again become mutually intelligible under certain circumstances. [...]. I know by experience that, in the city of Hamburg, where though the polite and literary speech is High-Dutch, the natural speech of the people is Nether-Dutch, if you speak English slowly and carefully, choosing your words well and uttering them distinctly, you will be understood by a common man in the streets of the Hanseatic city.
Source: wiktionary
But round about these, in a broken curve are found the represenatives of the Low-German (Nieder-Deutsch, Netherdutch or Netherlandish) family. Along the shores of the Baltic and far inland, where German [= (Standard) High German] is established in the educated ranks, the mass of the population speak Platt-deutsch, which is nothing but a form of Dutch, not German or Hoch-deutsch.
Source: wiktionary