I have this problem with my
wife's mum... She speaks really quickly, and whenever I ask her to repeat what she's just said, she just says what she said equally quickly, but with long breaks between the words - so it becomes "what'cha (pause) wanna (pause) do (quizzical look)?"
It's a real skill being able to simplify your native language so that learners of that language can understand. One of my wife's friends is really good at it - first he repeats what he said with slow and careful pronunciation, and then, if I'm still having difficulty understanding, he'll use simpler sentences to convey the same meaning. My wife, on the other hand will just get frustrated and speak to me in English. Warui sensei desu!