I can't follow you. 我没听懂。
1. I can't follow you when you speak fast.
2. Hold it. I can't follow you.
3. Do you know what I'm saying?
A: Do you speak English?
B: Yes, a little.
A: Can you tell me how to get to the Jade Buddha Temple?
B: I'm sorry. I can't quite follow you. Would you mind speaking slowly?