The language
The King James Version was translated in 1611, and some of its English has changed meaning since. The good news: the patterns are few, and once you learn them, the language opens up — and its precision becomes a gift.
A helpful habit: read the KJV aloud. Its rhythm was made for the ear, and many "hard" sentences become plain when spoken. And when a word still puzzles you, comparing the verse in a second translation is not cheating — it's study.