She doesn't understand you.

Source: Tatoeba

I can't understand what you're saying.

Source: Tatoeba

I couldn't understand his joke.

Source: Tatoeba

Tom said something that I didn't understand.

Source: Tatoeba

I did not understand him at all.

Source: Tatoeba

I couldn't understand him at first.

Source: Tatoeba

I cannot understand my school mate's Cantonese.

Source: Tatoeba

He's a foreigner. He doesn't understand what we're saying.

Source: Tatoeba

I'm sorry, I do not understand. Can you repeat it a little slower?

Source: Tatoeba

Tom always speaks in such a low voice that I can barely understand what he says.

Source: Tatoeba

I can understand most of what they say, but I don't understand the slang they use (in their speech).

Source: Tatoeba