I would like to create a VPN server in OpenWRT but I have no idea how to start.
What services are currently available and which are recommended in each case?
I have a TP-Link Archer C60.
And what do I do with that?
Click on the OpenVPN Basic page.
For getting started through proof of concept "lab" testing (i.e. two devices connected in a LAN with no link to the Internet), you can start with no certificates and a simple password authentication. I suggest creating your certificates on a PC rather than on the router.
I already entered the page but I do not know what commands to start with.
It is not a simple project. You should be familiar with logging into the command line, editing config files, creating interfaces and firewall rules etc.
The official OpenVPN wiki and FAQ will also be useful. It is best to write a native ".ovpn" style config file to control the OpenVPN process directly.
I know how to open the configuration files, such as network and wireless. What I do not know, is what to put on them.
Not to sound like an a-hole, but did you read the documentation?
Yes, but I do not understand the content and explanation of OpenVPN Basic. On top of that, I do not speak English. I use google translate.
It is more a primer about how to setup OpenVPN. Read the comprehensive section of the wiki for an in depth configuration.
General information on OpenVPN is here:
https://community.openvpn.net/openvpn/wiki
You could first try setting up a client of a commercial service to get a general idea how VPN works. The "vpnbook" service is free though I wouldn't trust them to anything actually private.
I'd better leave it because it's very difficult for me. Same thanks.