To fix this, you will need to change the language in Steam itself.
On the Steam menus, right click on the game and go to 'Properties'. In the top tab bar, go to 'Language' and then change to 'Italian'. This will download the Italian language pack for you.
Should work from there
Here is a temporary solution until what you've reported can get fixed:
1. Find the F1 2019 folder (Default location: Steam Folder/steamapps/common/"F1 2019")
2. Navigate to F1 2019/audio/2019/speech
3. Rename all files that start with en_ to something else
4. Rename all files that start with it_ to start with en_
This means that you've renamed the Italian voice files to the English ones, but this may cause issues, and if you encounter any, please revert the changes.
If you do not have the language specific files, try to change your language to English and then back to your preferred language 🙂
Workaround - Only to be used in cases when nothing else works!