This could be quite a long one. The English language is a mixture of various languages (German, Dutch/Frisian, Scandinavian languages, French, Latin, Greek etc). English has evolved since Anglo-Saxons (now Netherlands and northern Germany) and Angles (southern Denmark) settled in south and eastern England. Over time different groups of invaders came and bits of their languages were adopted. At the same time, England became a united kingdom under Alfred the Great and then the rest of the island (and nearby islands) got conquered and other languages were pushed to the fringes (e.g. Welsh, Cornish, Scottish Gaelic). The USA speaks English largely due to the significant numbers of English speakers (from England, Scotland, Wales and Ireland) that settled in the Thirteen Colonies and signed the Declaration of Independence. The USA doesn't have an "official" language, although English is the most widely spoken and is the "main" language used by the state.
Quick is an adjective (a describing word), for example - "Usain Bolt is very quick!" Meanwhile, quickly is an adverb (modifies or qualifies a verb) - for example, "Usain Bolt quickly ran the 100m".