German phrase
Das habe ich nicht verstanden.
Meaning
I didn't understand that
When to use it
You did not understand. Use it to politely ask for a repeat.
Example dialogue
Der Zug fährt um 18:30 ab Gleis 7.
The train leaves at 6:30 p.m. from platform 7.
Das habe ich nicht verstanden. Können Sie das bitte wiederholen?
I didn't understand that. Could you please repeat that?