And i have a second question:

When a user is connected to the router by VPN, Omada is not showing the device in the device-overview. Why? 

  @ChristianSchaaf 

you need to create a route where the next hop is the remote OpenVPN ip

SORRY this only work if you use Wireguard as Client on computer. 

  @MR.S 

Thank you for your reply.

I assumed that i have to create a route. But i don´t know how to do it. Can you help me? 

In the configuration there are the settings for the routing. I can choose between static route and policy routing. Here you ca find 2 screenshots. It looks different to your screenshots. 
 

  @ChristianSchaaf 

I'm sorry but it only works if you have wireguard as a client, I tested a bit with the setup you have with openvpn on pc but then the routing wouldn't work.

My setup is OpenVPN between two routers and wireguard as the client on pc that connects to wireguard server.

so if you have the opportunity to set up a wireguard server it will work.

routing is configured like this

  @ChristianSchaaf 

Ok I get it to work with OpenVPN to, you have to route to your OpenVPN IP Pool to like this. this is IP Pool in your Server config that client connet to

  @MR.S 

Hi

i will try it! 

But just to be sure... in your example, the 10.20.1.1 is the IP of the router (wireguard server and OpenVPN Client) and the 10.93.5.1 is the IP of the server (OpenVPN Server)? Or is the 10.93.5.1 the router and 10.20.1.1 the server? 

  @ChristianSchaaf 

I wrote it wrong, 10.20.1.1 should be 10.20.1.0/24 that is remote LAN

10.93.5.1 is remote OpenVPN server ip address

and 10.77.88.1 is OpenVPN server that client connect to and this serveren is configurert with full tunnel mode, if not full you have to add remote network in server config to.

Good luck with the project :-)

  @MR.S 

Let´s do a example please. 

On the Omada Router i have these Open-VPN-Server-Settings: 

If i connect with a client, the client gets the 192.168.98.20 for example.

And here is the config of the Open-VPN-Client on the Omada router for the "jump" to the server 80.82.218.154

The Omada router receivs the following IP.

Now i´m still not sure, what IPs i have to fill in for "Destination IP" and "Next hop".

Thank you! 

  @ChristianSchaaf 

In this example I have connection to remote network with ip 10.20.2.0/24 that is routet to 10.93.5.1 and second line is routeing to local OpenVPN Server to get comunkation both way fro 10.20.2.0/24