what they're saying

I can't hear what they're saying.

Je n’entends pas ce qu’ils disent.

I understand what they're saying.

Je comprends ce qu’ils disent.

I don't always understand what they're saying.

Je ne comprends pas toujours ce qu’ils disent.

I'm having a hard time understanding what they're saying.

J’ai du mal à comprendre ce qu’ils disent.

I hear through the wall what they're saying.

J’entends à travers le mur ce qu’ils disent.

It's true then, what they're saying on the train.

C’est donc vrai, ce qu’ils racontent dans le train.

— Harry Potter and the Philosopher's Stone (2001)

I can't always understand what they're saying.

Je ne comprends pas toujours ce qu’ils disent.

I don't understand what they're saying.

Je ne comprends pas ce qu’ils disent.

I'm not sure what they're saying, but they're gonna fight.

Je ne sais pas trop ce qu’ils disent, mais ils vont se battre.

— Happy Together (1997)

I don't know what they're saying, but I know they're speaking French.

Je ne sais pas ce qu’ils disent, mais je sais qu’ils parlent français.