This file must be writeable: modules/mod_newsletter/inc/lastcompleted.txtOpen Elxis error log and copy-paste here the error message the module generates. Elxis administration : Site > Logs > error.log
If it is not writeable you will receive multiple emails like you did.
To stop sending emails you don't need to unpublish the module. You can set it to "collect subscriptions only".
What you mean it doesn't work in Italian? The messages within the e-mail text are written in the subscriber's preferable language. If he has no language preference the messages are written in English.