Can anybody explain the difference between "mit" and "mi"?
"mi" is just "what." If that becomes the direct object, you need to use accusative case, so it becomes "mit."
It's like the difference between using "der" and "den" in German, except it affects the noun, not the article.
And here we have "művésznő"--a woman artist! I thought we needed to start seeing a little more of this. Köszönöm, Duolingo! You're a good owl.