It is not an idiom. Idioms are expressions whose meaning cannot be derived from the meaning of the words in them. The meaning of the expression " to have an open mind" is perfectly clear.
It means to keep from making decisions without knowing all of the facts. A closed mind is one that is made up before the person knows all the facts. If you have an open mind, you are receptive to new ideas. If you have a closed mind, you are usually prejudiced and judgmental.
It means being free of intellectually bigotry and being tolerant of disparate ideas and opinions, as well as demonstrating a willingness to listen and understand -- but necessarily accept -- different or even eccentric points of view.
A person with an open mind doesn't reject an argument or an opinion before he hears it. He doesn't decide that something is bad or inferior because it's new or foreign to him. And he understands that different people will look at a situation and come to opposite conclusions based on their own personal perspectives, priorities, and proclivities.
It's not really an idiom. It means "what are you thinking about."
You're out of your mind means your ideas are crazy.
Cleaning ones mind of misunderstanding
Mind your Ps and Qs means to use good manners.
The idiom, "You lost your marbles," means that you've gone crazy.
"Loud of your mind" is not a common idiom. It likely stems from a misunderstanding or misuse of the idiom "out of your mind," which means to be crazy or irrational.
to make a bad thing worse
It means you have one eye open. If you mean the idiom "sleep with one eye open," it means that you are staying alert at all times in case of disaster.
That means answering with the first thought(s) that come(s) to mind.
It means to be more concerned about what you are doing than checking on what others are doing.
It's not an idiom, it's a computer direction. "Opening" an attachment means clicking on the link and causing the attachment to upload to your computer.
"Out of your mind" is an idiom. It makes no sense unless you already know that it means you are behaving in a crazy manner.