Translation:In the library the teacher writes inscriptions in German.
"The teacher writes German inscriptions in the library" was marked incorrect.
The word order is unnatural, the main translation in English should be "The teacher writes inscriptions in German in the library" or "The teacher writes German inscriptions in the library"
My thought would be that the sentence would have to be "inscriptiones germanicae" with "germanicae" being an adjective modifying "inscriptiones" to be "German inscriptions." In this sentence, "germanice" is in the ablative showing how the inscriptions were written "in the German (language.)"