I can't understand
No puedo entender nada de lo que dices.
I can't understand anything you're saying.
Yo no puedo entender qué es lo que él está tratando de decir.
I can't understand what he's trying to say.
Hablas demasiado rápido y no puedo entender todo lo que dices.
You speak too fast, and I can't understand everything you say.
Lo siento pero no puedo entender lo que ha dicho en inglés.
I'm sorry, but I can't understand what you've said in English.
No puedo entender lo que pasó.
I can't understand what happened.
I can't understand what you're saying.
I can't understand.
Hablas tan rápido que no puedo entender una palabra de lo que dices.
You speak so fast that I can’t understand a word you’re saying.