Custom sidebar on mobile

I need to view the sidebar only in the categories. Not in posts. It’s possible?
Thanks

Not function for the categories.

No, maybe I explained myself wrongly.

I would like the desktop sidebar to be displayed also in a mobile version.
I inserted in the sidebar “most read” and I would like them to be displayed also on mobile, under the list of posts of the category (only in a category pages).
Thanks

Yes.
Made of a responsive size.
It’s possible?

Is it not possible to make it visible and adapt it to 100% width? On mobile device.
That’s what I’m looking for my theme…

Yes, right after the content. But only in the category pages. Not in posts.
What code should I use?
Thanks for support

Thanks a lot.
I changed the code to:

@media (max-width: 990px){
        .category #secondary{
                display: block !important;
        }
}

Thanks for your support

(I’ll wait for the rss fix in the categories to activate the theme on my site)