As I advised in my previous reply on a different thread, I think you should read the following section to get some basic information about Buddha Dhamma:
“Moral Living and Fundamentals”
But to provide some quick answers.
“Once an arahant passes into Nibbana, does it stop having a mind or does the mind follow its evolution and this evolution would be Nibbana? Can we properly speak of an enlightened mind?”
– An enlightened mind (that of an Arahant) is a mind devoid of greed, anger, and ignorance (about the true nature of this world). That means that one will be stuck with the rebirth process as long as one has no comprehension about the Four Noble Truths.
– When one truly understands the Four Noble Truths, one will see that there is much suffering in the future especially due to rebirths in the four lower realms. Those rebirths arise due to akusala kamma done with greed, anger, and ignorance.
– That is why it is important to understand how the laws of kamma work first.