Wordpres Nav menu in header and sub menu in sidebar

Hello Dear Bloggers,

i have a query and i know that you know the answer of this
i am using wp nav menu to show 6 navigation menu in header here
https://showprojects.net/projects/csrc/

Now i want when user clicks on any item(post,page,category,tag) in sub menu then the left sidebar will show all the submenus of that parent.

My question is similar to this thread
https://wordpress.stackexchange.com/questions/2802/display-a-only-a-portion-of-the-menu-tree-using-wp-nav-menu

Explaination
Root Menu
Sub menu 1
Sub menu 2 (clicked)

My sidebar will show only child sub menus of clicked root menu
Sub menu 1
Sub menu 2

Waiting for your answer.
Thanks
Vaseem Ansari