Hey Jean,
I wanna help but I don't know what to do... I still don't know the structure of moodle :D ... I'm a Joomla professional(admin)... I can translate this block files into Arabic, also I will post my modified index to share ideas...
But wondering I have changed some strings on blocks/verify_certificate/lang/en/block_verify_certificate.php
but it doesn't take effect is there is something I should do after modification!! or there is something elsewhere overwriting it !!!!!?
Thanks