Wireguard Site-to-Site VPN to Azure server

Hi folks,

I've tried it before and failed and now I'm hoping that someone here has done it before. I want to set up a site-to-site VPN with Wireguard to monitor my unRAID server with all its services and Docker containers from the outside, even if the power is out at home etc. I also have a small Linux server at Azure for this purpose and would like to connect my local unRAID server and the Azure VM.

I've done everything you're supposed to do according to normal tutorials, but it just doesn't work. I have also enabled port 51820 for WireGuard for my unRAID server in my router (FRITZ!Box). LAN to LAN access should be right I hope.

Then I used DuckDNS to secure a domain just for this purpose.

unRAID Config:

This is my container config in Azure (port 51820 in Azure opened as well):

services:
  wireguard:
    image: linuxserver/wireguard:latest
    container_name: wireguard
    cap_add:
      - NET_ADMIN
      - SYS_MODULE #optional
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Europe/Berlin
      - SERVERPORT=51820 #optional
      - SERVERURL=private...
      - PEERS=1
      - PEERDNS=auto
      - INTERNAL_SUBNET=10.13.13.0
      - PERSISTENTKEEPALIVE_PEERS=25
      - LOG_CONFS=true
      - ALLOWEDIPS=0.0.0.0/0
    volumes:
      - /media/appdata/wireguard/config:/config
      - /lib/modules:/lib/modules #optional
    ports:
      - 51820:51820/udp
    sysctls:
      - net.ipv4.conf.all.src_valid_mark=1
    restart: unless-stopped
    networks:
      - azure

networks:
  azure:
    external: true

And I have this wg0.conf in my Azure Wireguard Container:

[Interface]
Address = 10.13.13.1
ListenPort = 51820
PrivateKey = private IDK where its from
PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -A FORWARD -o %i -j ACCEPT; iptables -t nat -A POSTROUTING -o eth+ -j MASQUERADE
PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -D FORWARD -o %i -j ACCEPT; iptables -t nat -D POSTROUTING -o eth+ -j MASQUERADE

[Peer]
# peer1
PublicKey = public
PresharedKey = preshared
AllowedIPs = 10.13.13.2/32

If you read on the internet it should be simple but I cannot achieve what I want.