how do i get my sidebar above content on nanomag theme

You could use some absolute positioning CSS for that media query for that class that displays the sidebar. It all depends on how the theme code is written, as does the actual name of the class that the theme uses. One tutorial on that subject is here: https://www.w3schools.com/css/css_positioning.asp

You might be able to put your CSS in the Custom CSS of the Theme Customization, making sure you add the proper media query statement so it doesn’t affect other screen resolutions. Otherwise, you’ll have to do a Child Theme, so you don’t mess with the theme’s CSS.