Expand/Collapse Menu

Hello everyone,
My name is Lynda.
I try to create a menu which has several categories.
When a categogy is clicked, a submenu will be open.
Then another category is clicked, another submenu will also be open. The result is: I am getting a long, long menu after all categories are clicked.

Would you please direct me a technic when a new category is clicked, a previous opening category will automaticlly be collapsed.
Thank you very much and I am look forward to hearing from you.
Lynda.