"What is your question?"
"Can you repeat your questions?"
"As compared/supposed to what?"
"Please send sufficiently in advance so that I could have time to go through the questions before meeting." It's hard to understand complex questions without knowing the context and technical details.
Please send in-time emails whenever you have questions rather than wasting time going wrong directions.
"It's not a good use of your time."

• "I see." - "I don't see! Please explain clearly ..."
  "That does not make any sense to me."
  "Sorry, I'm totally lost. Please go back to the beginning, the very beginning: What's the purpose of the system? What's the data? What's the your method? What's your proposed way of evaluation? What's his evaluation? What's the problem?"