OnlyOffice with Docker and Apache2 as reverse Proxy

Hello

Im new to onlyoffice, but not to nextcloud / linux server.
Actually im trying to integrate the onlyoffice/documentserver docker image into nextcloud.

On my docker, there is a apache2 reverseproxy instance.
I started onlyoffice with -p 444:443. i also generated some self-signed certs and placed them in the right folder.
If i enter https://IP:444 then it works without any problems.

If i try to forward all requests through my proxy, i get an “internal server error”.

This is my proxy config:

<VirtualHost *:443>
SSLEngine on
SSLCertificateFile /etc/httpd/conf.d/ssl/server.crt
SSLCertificateKeyFile /etc/httpd/conf.d/ssl/server_priv.pem

ProxyPreserveHost On
ServerName ......
SSLProxyEngine on
SSLProxyVerify none  
SSLProxyCheckPeerCN off
SSLProxyCheckPeerName off
SSLProxyCheckPeerExpire off

ProxyPass / https://InternalDockerIP:444/
ProxyPassReverse / https://InternalDockerIP:444/

</VirtualHost>

Unfortunately, the above config seems to be invalid.
Can someone share his config with me or give me a hint, where to search for the mistake?

Thanks.

have you configured the ssl certificates in the onlyoffice container?