Site broken: vars.php(34) : runtime-created function

I suspect your website has been hacked. My recommendation: first read this article:

FAQ My site was hacked

After that, I would recommend checking whether you still have a clean backup. If so, delete all files and the database and restore the backup. Then change all access data in the hosting.

If you do not have a backup, you could try to replace all WordPress core files manually. The procedure is described here: https://wordpress.org/documentation/article/updating-wordpress/#manual-update

Finally, you should secure your project. This is described in more detail in the article here: https://wordpress.org/documentation/article/hardening-wordpress/