Kaltxì, ma Ateyo Alayon ulte zola'u nìprrte'! (Hello, O Ateyo Alayon and come pleasantly!)
You have indeed found thr riht place to learn the Na'vi language. Every resource you need is here. There is a relatively small but tenacious group of folks here who will be happy to help you learn, and chat in Na'vi with you. (There are places to do this, both in writing, and in speaking.) It's also a place to just hang out with likeminded Avatar fans.
Don't feel bad about mistakes; we all make them, even those of us who have been doing this for years. And I don't think your English skills or lack thereof will be a big problem here (although we have not had a lot of Italian folks here).
On an unrelated note, I hope the big earthquake they had there a few days ago didn't affect you too badly!