The story isn't hard to follow...the bad editing, however, is.
It feels like it's trying to make the story more grand than it actually was. All the unnecessary scenes and twists to try and be more clever. Look, a grab from nowhere twist (going against prior lore, more on that later) isn't clever or smart; it's a trick. It's the cheapest trick. Even if the editing was good, it would still feel like there were so many unnecessary points.
Like when they do two parts of one book... everything feels stretched.
As for lore;
Look... I'm not huge into the Potterverse...but I enjoyed the books and films. Even with my passing knowledge of the lore, I couldn't help but be confused by the new magic being shown that goes against previous rules or just exists.