Theme fatal error

My Theme is not working anymore.
Wordpress send me this error code:

WordPress versie 6.0.1
Actief thema: Mesmerize PRO (versie 1.6.142) Huidige plugin:  (versie ) PHP versie 8.0.20

Foutdetails
===========
Een fout van het type E_ERROR werd veroorzaakt op regelnummer 10 van het bestand /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-content/themes/mesmerize-pro/functions.php. Foutmelding: Uncaught Error: Call to undefined function create_function() in /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-content/themes/mesmerize-pro/functions.php:10
Stack trace:
#0 /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-settings.php(566): include()
#1 /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-config.php(96): require_once('/var/www/vhosts...')
#2 /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-load.php(50): require_once('/var/www/vhosts...')
#3 /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-admin/admin.php(34): require_once('/var/www/vhosts...')
#4 /var/www/vhosts/wesdorpsloopwerken.nl/httpdocs/wp-admin/index.php(10): require_once('/var/www/vhosts...')
#5 {main}
  thrown

Already tried to change the version number in the editor but it didnt work.

Also i get this error: This theme failed to load properly and was paused within the admin backend.

Hope someone can help me!

thx