@PseudoKirby:
and does oda create the chapters weekly? or does he pile them up then slowly release them
With regards to this, Oda does work at the pace of approximately one chapter per week. It's not exactly clear how far ahead of the magazine he actually is, but I would imagine that it's no more than a couple of weeks at best. Oda seems to be good at keeping to his deadlines, whenever they are, so it's harder to judge compared to if he wasn't. (Take, for example, Naoko Takeuchi, who was always working past deadlines with Sailor Moon, or Yoshihiro Togashi, who actually had to turn in draft versions of some Hunter x Hunter chapters: for them, it's obvious that they were behind; it's harder to tell just how far along the manga is when the artist is ahead.)
also, why arent they longer? I have heard that an anime eps of one piece is like 1 - 3 chapters of the manga, couldnt this solve the filler problems if they just make the chapters a bit longer so that they even out?
Aside from the obvious amount of work that goes into any single chapter of a weekly manga, such as the need for storyboarding, scripting, sketching, etc. well before the final draft, inking, tone, and lettering… there's a generally accepted length of a Weekly Jump chapter that seems to fall somewhere between 15 and 20 pages per issue (One Piece is 19 pages per chapter, including the title page). Special chapters (including first chapters) can be longer, but these are exceptions rather than the rule.