Thank you very much kurtsteiner for your answer and your excellent sens of humour !

Hard to stay serious after such an answer lol
In fact, it is realy strange :
Finaly considering what you took time to explain, if :
- I install joomfish
- I install additional languages to joomla
- I don't install special xml files for Gj support
- I switch languages from the frontend module of joomfish
It should work (even if categories, descriptions and groups are not translated) : groups should be visible.
On my website, considering these parameters are ok, I can't access to groups I created !..
I'm wondering If it is a question of versions (I use Joomfish 1.8 rc and Gj 1.6 bĂȘta 3).
I would like to show you (my website is
www.euro-friends.com), but gj functions can only be seen by backend managers until I solve the problem.
Thanks a lot for your help !