Gheebat and Mocking

Does making fun of another language result in making fun of the signs of Allah

Q: "And among the signs of His power is the creation of the heavens and the earth and diverse language and skin color. Surely, with that situation actually there are signs for people who know" (Ar-Rum:22)

According to an intrepretation. If I make fun of someone speaking in other language which seems funny, is it as if I made fun of a language (Allah's sign) and thereby kufr?

Backbiting

Q: Is it kufr to backbite a Muslim to a non Muslim? Also is it kufr to complaint against a Muslim to a non Muslim if he has harmed you for the purpose of correcting him so that he doesn’t do the same mistake again?