Apache2 Proxy

Hello there!

Can someon help me setup Nextcloud signaling server behind an univention server. My Univention server would be the public facing webserver. I set up may signaling server hopefully fine.
BUT I can’t figure out the virtualhost on univention.
My config currently is:

<VirtualHost *:443>

# ... existing configuration ...

# Enable proxying Websocket requests to the standalone signaling server.
ProxyPass "/standalone-signaling/"  "ws://"

RewriteEngine On
# Websocket connections from the clients.
RewriteRule ^/standalone-signaling/spreed$ - [L]
# Backend connections from Nextcloud.
RewriteRule ^/standalone-signaling/api/(.*)$1 [L,P]

# ... existing configuration ...

But I only get an 404 error. (I already enabled the site)