Submenu WordPress

I call you for help because I took over a site or all the links of the menu was hard in the header.php
I start to make the whole dynamic but I encounter a problem, the submenu …
I look for I can not find anything can you help me?

I want the same sub-menu of your theme : https://www.ads-software.com/themes/silk-lite/

The Website : https://rd-affutage.pexys-studio.com/