Hi Giraffeso,
Here's how to change the language back to English:
-Click on the Messenger Plus! icon.
-Click on "Preferenze & Opzioni"
-The "Preferences and Options" menu will open
-Expand the "Lingua" menu.
-Click on "Lingua Interfaccia"
-Click on "English" and then "Applica"
-If it asks to Restart, press Yes.
Hope this helps.