Ethernet, WiFi 2.4 and 5GHz would indeed have other addresses. There's nothing wrong with that.
Your post has not enough detail about your ISP and more that I'll just write there is nothing wrong with 6 MAC addresses given the story.
My internet service provider offers limited device access to the internet so I have connected my main PC through Airport Express with the wires and internet works ok, but not WiFi as 2.4GHz and 5GHz frequency WiFi have a different MAC address from Ethernet MAC address.
Is it some solution how I could get the Wifi internet at this stage