I need to copy a website that needs 2 form authentication.... It's my
modem/router config page and all it's content and half of it are .asp pages
(I've read they are tricky because the things are processed and populated from
server side or something like that that I Don't understand well). First, it
asks the password in an "authentication form" and after that again asks
another authentication to access the admin mode in another authentication
form; but this time there are two fields in the form: user and pass (the same
pass as the first). I have both and I can surf normally. 
I also have enabled http and https acesses and ftp, and ssh. (I dont know what
can I do from there because it doesn't support any commands that I've tried
(not even "ls" or "help")... nothing except "set" that only works for pretty
simple things like change the wifi channel, SSID and wifi password and things
like that... Although I've never loged in into a system via ssh and only used
ftp to download things on a browser but it doesn't look like I can access to a
directory tree... That would be a start).
My goal is to be able to study the codes and modify some config pages that
don't work properly (like fixing the DynamicDNS option that doesn't work for
some of the 5 providers that supports by default and for others just gives a
popup that says that some /cgi-bin/archive.xml can't be updated, and another
doesn't exist anymore), maybe if possible tweak it to add more providers to
the DDNS list that I have working (or at least add a simple line that connects
to the API via an URl to update the ip), or multiple DDNS at the same time,
and enable some features that are locked by my isp ( like changing their
default and awful DNS that they locked to change it for my NextDNS account)...
and ,who knows, maybe change or add something better than the awfull GUI.
I don't know if I can do something with the ftp or ssh.
And dont know what should I do to configure the Httrack for this 2 "form
authentications".

And I can't even find the option for authentication in the Android app!!

Can the auth proxy be done on the Android app, or can I create the URL and the
archive related manually? What would be the format and what tool should I use?
( I could use a linux terminal that I have installed with Termux)

I appreciate any guidance or help that you could give me (for any part of my
trouble) at least for the learning experience!

Thanks in advance!