Ok, I managed to do it : )
I installed a plugin (“Topics Per Page (0.0.7)”) for reducing the number of the latest discussions’ posts and I changed in my template, in the front-page.php file, the order in the of the two tables (latest discussions and forums).
Finally was easier than I thought : )
I did it.
I thought it would be more difficult than it was.
An old version of joomla and an old forum called joomlaboard.
I dont know a lot as I m new to all this stuff, doing my internship here.
Thanks for the tip,
sometimes for people without experience (like me), it’s difficult to think even this