LFG; Lexical mapping theory; Lexical-functional grammar ; Syntactic development; Morphological development; Morphologie (Spracherwerb) ; Syntax (Spracherwerb) ; Grammatical development ; Transfer (second language acquisition) ; Transfer (Zweitspracherwerb) ; Cross-linguistic influence (second language acquisition) ; Interference (second language acquisition) ; Processability theory; Language comprehension (second language acquisition) ; Second language acquisition in children; Kindlicher Zweitspracherwerb; Child second language acquisition ; German ; English