I have worked for many years in translation, lexicography, and language education, and I am flabbergasted at how well ChatGPT handles natural language. It can produce example sentences of polysemous words as well as or better than an experienced dictionary editor (i.e., me) [1], and it can correctly guess the meanings of unknown words from very limited context [2].
Teaching an adult human to use a second language without making grammatical mistakes is nearly impossible, and native speakers often make mistakes as well. In a week of testing, I have yet to see ChatGPT make any grammatical mistakes in either English or Japanese. Like many native speakers, however, it is often not able to explain its grammatical instincts correctly [3].
[1] https://www.gally.net/temp/202212chatgpt/dictionarydefinitio...
[2] https://www.gally.net/temp/202212chatgpt/unknownwords.html
[3] https://www.gally.net/temp/202212chatgpt/explaininggrammar.h...