You can start by subscribing to Viz Manga's online platform or buying physical copies of One Piece from authorized stores. Then, just open the manga and start reading from the beginning!
First, read the main One Piece story thoroughly as the cover stories are often related to it. Then, pay attention to the details in the cover art, like the characters' expressions and the background settings.
The One Piece anime usually lags behind the manga by a considerable margin. The production of the anime takes time to catch up with the ongoing manga storyline.
One common place to read One Piece manga is through online manga apps or websites that have licensed the content. For example, Manga Plus is a popular choice. Just make sure you're accessing it from a legitimate source.
You can start by looking on fanfic websites like FanFiction.net or Archive of Our Own. They have a large collection of 'One Piece' fanfics. Just type 'One Piece' in the search bar and you'll get a bunch of results.
Well, it varies a lot. If you're a fast reader and dedicate several hours a day, you could finish it in a month or so. But for most people, it could take a couple of months or even longer.