Ok, a very stupid "solution" to the issue that never pops up into my mind I'm posting just for other newbies like me: refresh the cache FROM BACKOFFICE after applying the changes to the code...any other newbie mean won't work 
Now Google is validating the changes, assessing whether they're effective or not. It says it will take some days for it.
I'll keep you updated.
@Daresh thank you for your prompt support! Very appreciated!