Often, the language files are already there, but the game is set to the wrong region.

“And you shall. But remember: just like in Dunwall, your choices have consequences. Don't just kill everyone. Try the low-chaos route. It’s harder to be kind when the world is broken.”

No. Saves are separate from language files.

He decided right then: he would play the low-chaos route. In a world of "hot" repacks and stolen bandwidth, he’d try to be one of the good guys.