Stick menu on mobile menu

Set it to position fixed
https://www.w3schools.com/cssref/pr_class_position.asp

What class/id controls the menu?

Do you have anything in the dashboard named, “Custom CSS”, “Custom Styles” or “Jetpack”?

Na, its a fresh install.

Download (and install) this Custom CSS Manager plugin and in its allocated section of the dashboard, enter this;

@media screen and (max-width: 650px) {
 .sb-holder {
  position: fixed;
 }
 .home #wrapper {
  top: 35px;
 }
}

Why not just do that in the css file?

Menu sticks, but looks like I need to modify a bit.

• When the theme updates, you’ll lose your changes
• Debugging becomes harder as you can’t differentiate between your styles and the theme’s original styles easily
• You can potentially harm the theme by modifying its original files