There has been a critical error on this website.

Try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and rename the directory of your currently active theme. Hopefully, this will force the default theme to activate and rule out a theme-specific issue (theme functions can interfere like plugins).

Hi! Thank you for your reply! Unfortunately, all of your solutions did not work. The weird thing is that you can open the homepage but not other pages or any page with an utm-parameter.
Is there maybe another way to fix the issue?

Ok, try downloading WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), and delete then replace your copies of everything on the server except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.

If you’d like to manually make a backup of your site first, please follow the steps at https://developer.www.ads-software.com/advanced-administration/security/backup/

Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.