I can't understand what you want to say.
I can't understand what you are saying.
I can't understand what you are saying.
I don't know what you are saying.
I don't understand what you are talking about.
I can't understand what it is you want to say.
I don't know what you are saying.
I haven't come to comprehend what you said.
I don't know what you're talking about.
I don't know what you are saying.
I don't understand the meaning of what you are saying.
I don't get what you are saying.
I don't know what you are thinking.
I don't understand what you are talking about.
I don't see your point.