The linguistic diversity along the High Scardus Trail is as high as the cultural diversity: along the trail you constantly change back and forth between areas with Macedonian, Albanian and also Serbian language. In the Dragash area around Brod and Restelice, "Goranski", a transitional dialect between the Torlak dialects of Serbian, Bulgarian and the northern dialects of Macedonian, is spoken due to the Gorans living there.
In general, the language spoken in the mountain villages does not necessarily adhere to national borders: for example, in the North Macedonian mountain villages of Veshala, Bozovce and Vejce, Albanian is spoken predominantly due to the Albanian minority living there, while in the southern Macedonian village of Brezovica, Serbian is mostly spoken. For most hikers who are not from the Western Balkans, this is very interesting - but for communication on the trail, this will be mostly irrelevant, since hardly anyone will be able to speak one of the languages mentioned. With English you will get along well in the cities like Prizren or Ohrid (and of course also in the bigger hotels on the trail) - but in the mountain villages and the small guesthouses you will rather communicate with hands and feet. Never mind: people in the Western Balkans are usually extremely friendly, helpful and very good at understanding "whole-body" questions. Nevertheless, they should not be too complicated, or in case of emergency someone in the village will be looked for who knows English or even German.
If this is too exhausting for you or if you want to learn more about the country, the people and the culture, we recommend, also because of the language barriers, to book a tour with a local guide through this website. This may mean a little less adventure (but still more than it is offered on most other European long-distance trails), but significantly more relaxation, knowledge and also safety in case of emergency.