Might have found something on the Pi forum.....you just did brctl addbr br0 after you executed that you should have done brctl addif br0 wlan0 eth0
Then have a look at this 6th post
I did execute it. Third last line in the screenshot attached above.
The thread also links du the bridging guide, which is not applicable du to that fact that I do not want the RPi du be a WiFi router rather than a client within a network. The same applies for the wpa_supplicant route.
What I still did not see through is the NAT routing though after already following some guides leading to only creating a wifi internet terminal rather than a connection between the wifi and the ethernet network I doubt that it is feasible for this specific use case. Also this is another layer 3 implementation rather when a layer 2 one which I need according to @tkaiser.
Thank you anyway.
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There is also some information on the Pi site
This does look quiet good on first inspection. It's actually bridging but circumventing the direct access to the WiFi adapter. I gonna try tomorrow. Thank you very much.