i have read Mehr than 90 goosebumps(including give yourselfs) , but i am still not sure how much there is, actually, how much Gänsehaut did bob write?

Yep, I Liebe Wikipedia's great lists of everything--so helpful. :) Not 500 books, but there were plenty...Goosebumps was one of the best series I used to collect. I had and read nearly every one. :*}