I know this must sound pretty stupid but i can't seems to get around this problem:

i installed XOOPS and to be sure of making it right i used the italian language pack as it's my first language. Then once setup was completed i entered the admin panel and changed the language to english but now the main page has some parts in italian and some in english. Any idea?

I can only suggest you go into the admin/system/modules and update the system module.

What exactly do you mean when you say half? Is it certain modules? Try the update system in the above referenced and see if that helps.

Quest

Is there an \english folder in every \language folder?
If yes, the files inside them are in English or Italian?

Modules will have separate language files and this will cause your site to be in it's current state of affairs if you for instance, upload a module that contains English only language files.

You can add all the system language files that you want, but only to a point. Since an XOOPS site is module driven and dependant, it is neccessary for all your modules to have the appropriate translations. In many cases, the moduke developer will specify what languages it has translated and what languages it needs help in developing.

You can always modify the laguage files yourself and then submit them to the module developer. At least you will know that your site is in good working order with your own language.

I hope this helps some.

i had to go through all of them in the admin section and change, didn't take long do