As Spain began to colonize more and more countries those countries began to develop slang which then resulted in the slang being an everyday thing so then it became part of the language so thats why every spanish speaking country speaks differently.
Visit museums/ art galleries
Go to a concert
Drink freshly squeezed orange juice
It's correct.
Estoy comiendo una manzana.
I'm eating an apple.
Hope it helps
I don't really remember, but i think it's que te hablar por telefono?