Sub Menu Problem expand

When I click in sub menu. It is not open/expand style ?

Suppose, My menus are

Then, Click on “Bootstrap Source Code >> Bootstrap Advanced”

Result is:

But I want when I clic on “Bootstrap Source Code >> Bootstrap Advanced”

It will result like

See my site sub menu link

https://coding.horje.com/category/bootstrap/bootstrap-advanced

Please give me a solution?

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