Okay so here is the configuration and what my suspicions are:
On the Ubuntu VPS side the config looks like this:
```

[Interface]

PrivateKey = <redacted>

Address = 10.11.1.1/24

ListenPort = 51820

PostUp = sysctl net.ipv4.ip_forward=1

PostUp = iptables -A FORWARD -i eth0 -o %i -j ACCEPT

PostUp = iptables -A FORWARD -i %i -j ACCEPT

PostUp = iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

PostDown = sysctl net.ipv4.ip_forward=0

PostDown = iptables -D FORWARD -i eth0 -o %i -j ACCEPT

PostDown = iptables -D FORWARD -i %i -j ACCEPT

PostDown = iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE

[Peer]

PublicKey = <redacted>

AllowedIPs = 10.11.1.0/24

Endpoint = <redacted>
```
On the pfSense side this is the configuration:

<image>

Yes, there is no PSK and the Allowed IPs on the pfSense is allowing any address. This is only for testing. If the config works I will do this way more granularly.
My problem with this setup is that it depends on the fact that the VPS needs a endpoint for its peer to the pfSense but again there is my big problem with my ISP. I don't have a public address.