Site menu is broken

A summary must describe what needs to be changed, and eventually why. A screenshot is not sufficient, even in the case a patch/MR is provided.
In the case of bug reports, the steps to reproduce the bug should be provided too.

The issue summary still shows just a screenshot without describing the bug or how to reproduce it.

Furthermore, is this bug only present in the 8.x-1.x branch?

@alok_singh

checked the Site menu Broken by installing Drupal 8.9.20 with "drupal/yg_medical": "1.0.0-alpha1"

Before :

After fixing :

By providing the solution in file web\themes\contrib\yg_medical\css\style.css

#main-menu .dropdown ul {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
box-shadow: 0 8px 16px 0 rgba(0,0,0,0.2);
z-index: 1;
}

/* Style the links inside the dropdown menu */
#main-menu .dropdown ul li a {
color: #333;
padding: 12px 16px;
text-decoration: none;
display: block;
}

/* Change color of dropdown links on hover */
#main-menu .dropdown ul li a:hover {
background-color: #ddd;
}

/* Show the dropdown menu on hover */
#main-menu .dropdown:hover ul {
display: block;
padding: 0;
}
#main-menu .dropdown:hover ul li{
list-style: none;
}