Flyout Menu in twentyfifteen

Hi All,

I am making a child theme to the twentyfifteen theme which will mimic my main site for my blog entries. However, my main site has a flyout menu and I am trying to recreate it in WP. I was looking at the generic https://www.cssterm.com/css-menus/vertical-css-menu/css-menu-flyout-left code and trying to implement it with my necessary changes but am having no luck. Couple of things:

1) I temporarily commented out code which makes the drop down button in the functions.php file.

2) When I hover over my menus I get nothing. But if I have the button on it will show the sub menu.

Is there an easy way to implement submenus as a flyout in WP modifying the twentyfifteen theme as a child? Any samples or code would be very helpful… I have already made modifications to the CSS to make it look like I want… Now just to get things to work.

Basically:

Menu Item 1
Menu Item 2
Submenu When Hovered
Submenu when menu 2 hover
Menu item 3

Thanks,