It occurs to me that this would be an useful phrase to politely decline someone who is trying to pry. I'm l a beginner, so it's hard for me know how to translate this.
“I am not at liberty to say” or “I am not at liberty to discuss”
(這個/ 這件事) 我不方便說 = (This/ on this topic,) I am not at liberty to talk
(這個/ 這件事) 我不方便討論 = (This/ on this topic,) I am not at liberty to discuss
'不方便' literally means 'not convenient' (as an adverb, it means ‘cannot conveniently) - it implies 'cannot freely'. It is a polite way to refuse to make any comment