@esprit 

You should connect your sky er115 to Internet port of the AX10 (use one of the ethernet ports on sky er115).

Now if you use your sky er115 as modem only (bridge mode), you can leave the AX10 in the default router mode.

If you use your sky er115 in router mode then it's prefererable to use AX10 in AP (access point) mode to avoid double NAT in your network.

Also, don't forget to turn off wi-fi on the sky er115 - if you don't it could lead to some wi-fi interference with AX10.

But in both cases you use the Internet poret (blue port) of your AX10 and one of the ethernet ports of the sky er115.

I any case you can tweak those settings with your ISP.

@esprit 

Hello, do you have internet access when you connect the sky er115 modem/router directly to your computer? If yes, you should be able to connect the AX10 to the sky er115 modem/router as instructed by Ivaylo. If you haven't tried this, please confirm this first as we can verify if there is any restriction or limitation on your line. If there is no internet access on the computer when the sky er115 modem/router is connected directly, while it works when the Sky Hub router is connected, there might be restrictions on your line and it is suggested to contact your ISP to release any binding.

Please refer to the below troubleshooting guide to confirm some basic settings again on the AX10 if the internet is working fine when the sky er115 modem/router is connected to your computer directly:
https://www.tp-link.com/support/faq/1556/