I asked my English teacher what is the difference is between...

I added an ellipsis (...) because it's an incomplete thought/sentence.

I asked my English teacher what is the difference is between people who improve their English quickly and peoplthose who improve their English slowly.

I asked my English teacher what is the difference is between people who improve their English quickly and people who improve their English slowly.

I asked my English teacher what is the difference betweena question.

I asked my English teacher w, "What is the difference between people who quickly improve their English quickly and people who are slow to improve their English slowly.?"

I askedAsking a Question to my English tTeacher what is the difference between

Usually, you want to give a preview of what your text is about with your title.

I asked my English teacher what is the difference is between people who improve their English quickly and people who improve their English slowly.