Why English is hard to learn

When I was young and smart, an American guy came up and asked:
“Hey, what’s up?”
“Um, the sky?” I replied.
Ages later, my hair grew grey, my brain became sluggish. An old American friend dropped by and asked the same stupid question:
“Hey, what’s up?”
“Um, I am alright,” I mumbled, ignoring what American guys cared up there.