Twenty Eleven Child Theme or Move Up Navigation or Access

I want to know how to move the top bar up in Twenty Eleven, like this website: https://www.wonderplugin.com/. I want to do what they did and use a slider like this.

I’ve added the CSS code I’ve found in other tutorials and it hasn’t worked. Is this something I can do through CSS edits? Do I need to learn something about php for this?

I’ve avoided PHP edits for Twenty Eleven and just done CSS edits for child themes here. I may consider hiring someone from the forum.

Thank you.