What i mean by changing the language is to change the language of everything that the visitors of my blog sees and read.
Ofcorse i know i can rewrite the posts etc to be displayed in my language, but for example the "Search" text displayed in the upper corner and such other details that cannot be changed from within the wordpress admin site.
Other examples are:
*The text that appears when you search for something and get no hits "No posts found. Try a different search?"
*The text related to comments, such as "One Response to “Hello world!”" and "user ¨¨Says¨¨: "
*Text on buttons, for example the "Submit Comment" text in the leave a reply area.
I hope this cleared up some of the confusion, sorry for beeing indistinct about what i want to achieve with this post.
Thank for helping me!