I found a thread in the documentation forum, and I think it is probably part of the soultion to what I seek.
http://www.phpwcms.de/forum/viewtopic.php?t=6553
I would like to have the possibility for visitors to choose between Swedish and English by clicking on a flag - or a bowl of porridge or whatever

But:
1. Do I have to make a extra installation of phpwcms to do that? I mean - do I install all files of v 1.2.6 in one called "sedish" and one called "english" ? The texta and layout and everything wil be the same - I just will make one english version of the swedish pages.
So I will need of course to translate the menu aswell, but so far I can't figure out how to do that without actually making two installations. If so - can they share database?