Study abroad program (language teaching) ; DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; Self-knowledge; Selbsterkenntnis; Self concept ; E-Mail; Voice mail; Chat; Computer-mediated communication ; Interview (communication situation) ; Students' language ; Identität und Sprache; Identity and language; Fremdheit und Sprache; Estrangement and language; Sprache und Integration; Integration und Sprache; Language and identity ; Second language acquisition (psycholing.) ; Case study (second language acquisition) ; German ; English