Hello Stefania80
Great!
Regarding the translation of the interface, this is a gettext / locale issue:
Either you've installed RosarioSIS on Windows and you should not have gettext (the PHP gettext extension) enabled.
See the php.ini section of the tutorial to enable / disable extensions.
Either you've installed on Linux and have not installed the it_IT.utf8 locale on your server.
To install a locale, check the installation tutorial (Other languages section).
If you didn't install RosarioSIS yourself, please ask your server administrator for help.