Hi. There's always more to be said, but check out some past threads:
Where did the structure of the week come from? Like, why are Saturday and Sunday a weekend? Why a weekend at all?: From over two years ago, a flaired user on alchemy and German/Czech history gives a short but accurate overview on the two-day weekend.
When did the world decide on a concept of a 7 day week, with 5 days on and 2 days off?: Also from over two years ago, a user looks at the origins of the seven-day week and the two-say weekend.
Why were Saturday and Sunday chosen as the weekend?: From an year ago, the same user as in the above thread briefly discusses the religious reasons for Sunday/Saturday being a "day of rest."
When did the current working week, Monday - Friday, become common place?: Also from an year ago, a mod discusses the reasons for the emergence of the Monday-Friday working week in detail.