State of the art ; Second language acquisition (language teaching) ; Zweitspracherwerb (Unterricht) ; Foreign language teaching ; Self-organization ; Multilingualism; Polylingualism; Plurilingualism ; English as international medium ; Bilingual education ; Zweitspracherwerb (ungesteuerter) ; Second language acquisition (untutored) ; Natürlicher Zweitspracherwerb; Second language acquisition