It's impossible language to learn because people keep making up new meanings for existing words. Nut is an extraordinary example here, apparently it can mean anything you need it to mean at the moment One can never learn English, one can only try to keep up.It's not. Also nuthead means something different. Nuts means something different again.
No idea why they say English is such a hard language to learn.
The language is hard because people who speak it make it hard. Deliberately, I suppose.