Grammerly has helped my writing for university tremendously to catch and correct mistakes that even my computer's autocorrect misses. However, the service is solely in English and my work is highly bilingual (French/English). The Grammerly software overruns my computers French autocorrect to "correct" my work in French into random English words with similar spelling. This has made it extremely difficult and stressful to write in French.
I don't expect Grammerly to be able to fully correct in other languages (although that would be incredible!), however the service needs to be able to at least recognize that a text is in a foreign language and allow the user to make their own edits accordingly.