LAB 14.2 OpenVPN problems

Hello again

I'm struggling this time with lab 14.2 and openvpn configuration

I followed all the steps in the lab exercise, however I can't run openvpn with

systemctl start openvpn@main

System returns error: Failed to start openvpn@main.service: Unit openvpn@main.service not found.
I've managed to run openvpn with

sudo openvpn main.conf and sudo openvpn secondary.conf respectively

After running like this, I can ping 10.8.0.1 and 10.8.0.2 from both machines
Firewall port 1194/udp on main is open and telnet server is running on secondary.example.com

When I login to secondary via
telnet 10.8.0.2

I can still capture all the traffic via wireshark on main (tun0) in plain text (?!)

How is this possible ? What am I doing wrong ?

I would also like to know why I can't start openvpn with systemctl as suggested in the lab...

Thanks a lot for your time !