I flashed a TP-Link Archer C7 V5 with "OpenWrt 19.07.0-rc1" as OS. This router is meant to replace my currently working FritzBox 7490. I've tried some of the examples in the OpenWrt docs for ISP configurations. But sadly nothing worked for me.
So maybe with giving you some information about my ISP and my location can help me figure out what I need to do. With your help of course.
¹) If the connection to a PVC (VPI/VCI) is not working, than you should use VLAN-ID 2011.
²) If the connection with VLAN-ID 2011 is not working, than you must use VLAN-ID 7. PVC-Values are not being used in both cases.
The Fritzbox 7490 integrates a VDSL modem and a PBX, but the Archer C7 does not have either of them.
Which device is going to provide these functions? Do you have a standalone VDSL modem?
The general recommendation however is to get a separate modem and hook up your OpenWrt router behind that. This way you are far more flexible in chosing a device that is supported by OpenWrt.
In case you need more detailed help in selecting a device, please head over to the Hardware section of this forum.
Why not use the FritzBox as a standalone modem and then use Archer as your primary gateway? Why do you want to have a single modem+router combo, any special reason?