You can download the website’s static files then (html, css, images, etc.) but features such as search won’t function if it works by querying some database.
Iirc most browsers have a way to make website’s available offline. I know chromium has it, but firefox does not. You’d probably need an extension for that. Or you can download the static files, store them in a directory manually and then open the index.html with firefox. That should work.
“functions on android”