Hi @maik282,
I have checked your website and found that the 404 page is coming. There might be some different reasons behind your issue, I would like to suggest troubleshooting the following common issue to help us to recognize the reason.
1.Theme Related Issue
2.Plugin Conflict
3.Theme Update related issue
4.Child Theme Related issue
5.CSS/JS Customization
6.Disabling Cache
7.Permalink
If you discover that an issue is coming from a custom code or 3rd party plugin, kindly consult with a developer or contact the plugin author. Please note that we do not provide support for custom codes and 3rd party plugins.
If none of the above helps, please copy your live site to a staging server so we can troubleshoot freely without breaking your live site.
And give us access in the secure note, including:
– WordPress Site URL & Login URL
– WordPress Admin username/password
To create a secure note, click the key icon underneath any of your posts.
NOTE: Please check by deactivating the Polylang plugin once, that might be the cause of your problem.
Thanks