do all animê start from mangá n so if it is succesful do most of the money go to the writer? (more similar perguntas inside) plzz answer

Well I'll answer as much as I can!
No not all animê start from manga. Sometimes there's mangá after the anime, or there won't be mangá at all. animê can also start from visual novels, like (i think) Chaos;Head or Steins;Gate!!

Not sure about the money, sorry..

And I guess it's personal preference whether you want to do a mangá or anime. For mangá you sort of have mais freedom, of what you want to draw or write and making your own characters could be fun, but it can be hard to get it published...
For animê you would most likely be drawing for other animes. So in their art styles and stuff (not too sure)

So yeah I hope I was sort of a bit of help! ^_^
(BTW you should read the mangá 'bakuman' talks a lot about creating manga, and it's entertaining!!)