Search:

Try:
Users
Altervista Data
Lingua: select "English" (see below image)
Click on "Cambia dati" (see below image)

https://i.imgur.com/CzgxBt0m.png
This should fix Update blog,...

Ok, but if you want all in english, you should register from international site: https://en.altervista.org

The demo comment, title and tagline like demo article are in Italian but you should have...

Hi, you can change language from the settings page: http://kgb.altervista.org/wp-admin/options-general.php Where you changed the language?
The default article still in italian but you should delete...