Avast says my router is infected because I'm hosting a webpage!?

Just because one of my devices has a webpage running on port 80 (that is secured by htaccess), it tells me my router is available through the internet!?

There should be further checks to verify that Avast really found a router there… (comparing the html data/interface).
And else it should just warn that there is a webpage running on my http port that could be my router (potentially).

An additional question:
Why isn’t there an instruction for AVM routers? They are the most sold brand in Germany as far as I know.

Just because one of my devices has a webpage running on port 80 (that is secured by htaccess), it tells me my router is available through the internet!?
Nothing wrong with the detection. This detection is correct or your website won't be reachable.
Why isn't there an instruction for AVM routers?
What do you mean? They all come with a manual.

The detecttion says my router (configuration) is accessible from the web which is apparently wrong, so the detection is not correct.

Take a look at the screenshots I attached.

No information how to do access the specific settings on a Fritz!Box router by AVM.

And the button access router settings in the first screenshot ends in a Firefox untrusted certificate warning.
You can of course access the Fritz!Box on its IP through http but AVM prefers it’s on web adress http(s)://fritz.box therefore the certificate is only issued for https://fritz.box but not for https://192.168.178.1

I think Avast has gone haywire. I pay Avast extra for Internet Security Scan. Yet I am getting a message that says my router is infected. but I’m using the Verizon supplied router with a lengthy password. I deleted a malware found, nothing else found. I notice that some of my neighbors have networks in range to mine. Is it possible Avast is picking up threats to them?

what is the exact message … you may post a screenshot