1. "Writing colony" is an uncommon phrase, but it just means a place far from a city where writers hang out together and write. Similarly, an "artists' colony" is a rural area where lots of artists live or visit.
2. The "staff" of a company is all the people who work for that company. Each company has one "staff", which includes all of its employees. Company A has 500 employees, and company B has 10 employees: company A's staff is much bigger than company B's.
3. so...that is a grammatical structure. "He is so [adjective] that [sentence]" means that he is very [adjective], and [sentence] is the result.
He is so fat that he can't fit through a door.
He is so smart that he can do math better than Einstein could.
She was so tired that she fell asleep as soon as she got home.
A slight variation is
he [verbs] so [adverb] that [sentence]
He runs so fast that even Usain Bolt can't catch him.
He eats so much that he needs special, large bowls.