I can build a page with three or four columns. The last column I will use as the right sidebar.

The problem is that the last column I turned into a right sidebar is not static, like the right sidebar is on a page without columns.

So, on a page I build with three or four columns, then turn the last column into a right sidebar, the right sidebar is not static and it looks weird on a mobile device.
This is because the content I put into the right sidebar now blends in with any content I put into columns 1-3, and its not showing last when scrolling through a page.

If I turn the last column into a right sidebar, I need two things:
1. When viewed on a desktop, I need the new right sidebar to be static.
2. When viewed on a mobile device, the right sidebar will show last…..after all content in the columns before it.

I mentioned that the sidebar is not showing when I create three columns.
I have also tried two columns, and the sidebar disappears.

What is the proper way to add columns to a page and keep a right sidebar?

Thank you for the reply.
Every time I add four columns, the right sidebar disappears.
I have not been able to have 3 or 4 columns on a page, and still have a right sidebar.