Made a mess with “WordPress Address (URL)” and “Blog Address (URL) in “Settings”

I have a site (elsatrento.org), and I have a(n empty) blog inside the site, at the address “elsatrento.org/news”, where “news” is the wordpress blog. I was experimenting with the General Settings and I did this: at the beginning I had, for WordPress URL, “elsatrento.org/news”, and for the Blog URL, “elsatrento.org/news”, and everything was fine. But then I put in WordPress URL “elsatrento.org”, and when I saved the page disappeared. Now every time I try with “elsatrento.org/news/wp-login.php”, a strange page appears where it asks me for the login and password, and then a blank page with “NO FOUND – The requested URL /wp-login.php was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.” shows up.

I hope I did not make anything beyond repair. How cai I fix it if I cannot even get inside the admin panel? Can someone help me please?