The fbackup.com website was translated to Polish by Global Poland. You can check out the newly translated version here: fbackup.com/pl (Polish)
If you want to help us translate the website (or the interface) in a language that's not yet translated in, you can start by visiting this page: Languages. You'll see here in which languages FBackup is not translated, and if you want to help you'll simply have to email us and we'll reply with details.