ce que tu essaies de dire
I think I understand what you're trying to say.
Je pense comprendre ce que tu essaies de dire.
I don't know what you're trying to say.
Je ne sais pas ce que tu essaies de dire.
Could you use an example to explain what you're trying to say?
Pourriez-vous utiliser un exemple pour expliquer ce que vous essayez de dire ?
I don't understand what you're trying to say.
Je ne comprends pas ce que tu essaies de dire.
Could you explain what you're trying to say by way of an example?
Pourriez-vous expliquer ce que vous essayez de dire en donnant un exemple ?