Language teaching ; Gastarbeiterkinder; Migrant workers (children of) ; Auswanderer (Kinder) ; Emigrants' children; Migrantenkinder; Aussiedler (Kinder) ; Kinder mit Migrationshintergrund; Immigrants'/Emigrants' children ; Bilingual education ; Case study (second language acquisition) ; Griechisch; Greek (modern) ; Modern Greek ; Early Modern High German