Applied linguistics ; Language testing ; DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; Dual language acquisition; Bimodal language acquisition; Spracherwerb (biling.) ; Language acquisition (biling.) ; Bilingual language acquisition ; Auswanderer; Emigrants; Migrant; Aussiedler; Gastarbeiter; Arbeitsmigranten; Immigrants/Emigrants ; German ; Turkish