Hi @valentina,
Sorry to hear about the problem you are having.
I have tested the latest version of Jevelin theme on my test site and it’s working fine for me.
I am not sure why you are getting this error.
Please delete the theme on your website using FTP or cPanel file manager and install the below latest version of the theme.
Please login to access this file
Also, please make sure you are using the latest version of PHP on your server by referring to the information provided in the following pages.
https://www.wikihow.com/Check-PHP-Version
http://php.net/supported-versions.php
Best regards,
Shufflehound team