Is it possible to make a mobile version of the site from scratch if there is already a desktop one?

Question

Layout

I'm making a site based on gulp/pug/sass(scss).
In general, I have a ready-made page that I have made, and I have a design for the mobile version of the same page.
There are a lot of permutations, it's easier to make a purely mobile version from scratch.
Is it possible? In fact, we catch the request to expand the screen and insert the desired template.
Or what's right? Tell me, thanks.

Answer 1

1) you can embed content on js
2) you can make css visibility / invisibility to do
Show screenshots can help