1. If I understand right, …
2. I'm sorry, I'm not sure I understand. Do you mean (that)…?
3. Sorry I don't quite catch you. When you say …, do you mean …?
4. I'm not exactly sure how to answer that question, but (perhaps)…
5. That's a rather difficult question, but (maybe)…
6. Could you please rephrase that question / topic?