Error analysis (language teaching) ; DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; Family communication ; Register (sociolinguistics) ; Sociolect ; Auswanderer; Emigrants; Migrant; Aussiedler; Gastarbeiter; Arbeitsmigranten; Immigrants/Emigrants ; Bilingual education ; Transfer (second language acquisition) ; Transfer (Zweitspracherwerb) ; Cross-linguistic influence (second language acquisition) ; Interference (second language acquisition) ; Second language acquisition in children; Kindlicher Zweitspracherwerb; Child second language acquisition ; German ; Turkish