WDS connection with an TP-Link Archer C6 v2

I just installed OpenWrt 19.07.4 on my TP-Link Archer C6 v2 and i was wondering how to use it as a WDS bridge.
Basically, I have a router from my IPS (H388X AGZHP_1.1.0) and I would like to have my Archer C6 as a WDS access point to expand my network.
I would be able to connect my Archer C6 via Wi-Fi to my main router to have internet access also on my Archer
I've not found step-by-step documentation about to
Any help?

That is most likely not going to succeed, WDS in general is not standardized. There multiple competing, incompatible, approaches to implement this functionality, the mainline linux kernel does this via 4addr, which is provided by the nl80211 stack shared by all contemporary/ relevant wireless drivers. Your ISP's router however is most likely based on a proprietary SDK with proprietary wireless drivers, which don't have access to nl80211 or 4addr and implement their own WDS variant instead (or none at all).

Alternatives would involve the 'routed client' setup or using relayd (relayd does not support IPv6 and comes with other more subtile issues).

I'm seeing this video https://www.youtube.com/watch?v=XW_V4W9lbj0

Do you think it's possible, somehow, to connect to the WiFi to the main router with my Archer C6 and uses that connection to give internet access via the ETH-ports? At the end of the day, I need only my workstation connected to the router as it hasn't a wifi card and the main router is in another room for wire connection