Responsive Website with a mobile-first approach using SCSS/Node JS/EJS

At the moment there are two issues with my app

• Whenever the user loads in a new item, my app reloads and the css is reset to default meaning if you are using the light theme, whenever you enter an item, you'll switch back to the dark theme. The only way I can think I can fix this is by using cookies. Is there another way to fix this?

• The other issue is the drag and drop. I have a version that enable me to drag and drop items but that's only on the user's end i.e when you refresh, it goes back to the default item order. My question is how can i modify the arrangement of my items in mongoDB since the list order is based on the order in the database.

Thank You for your help in advance :)