You don't need two installs. But you can try to force your Italian install to come up with English interface. Try the following. Exit Revit session and edit Revit.ini file in Revit Program directory. Find lines that look like
[Language]
Select=ITA

Change ITA to ENU, save ini file and start Revit again. Hopefully it will do what you are looking for. When ready to go back to Italian change back to ITA.