well, looking into the dokuwiki code I realized that the function auth_aclcheck of mod/dokuwiki/lib/dokuwiki/inc/auth.php is called with an empty $user and $groups variable, so for me it seemed as if I can also just get rid of dokuwiki's auth system by changing line 16 of mod/dokuwiki/lib/dokuwiki/conf/local.php into
$conf['useacl']      = 0;
that helps!
For the future it would be nice to be able to define read and write access for the wikis.

I wish i could just have some way to define that all first 'start' page of each group wiki, be on mode @ALL ---> Read access, without having to do this manually everytime i create a new wiki on a group. 

is there some workaround for this ?  

I dont get it how I can change the menu bar and navigation bar.