Stuck creating a dropdown menu

Hi,
I am trying to create a drop-down menu for the link list but I’m really stuck at this point. Every time I create a menu the whole navigation bar is messed up.

Can someone please assist?
Please see the following code I need help with. The menu is for the “School” list

Thank you in advance.

Ihttps://github.com/XavierJ96/SchoolWeb.git