How to buid wordpress menu with auto width sub-menu items in dropdown menu without any items sharing one line [closed]

You are not defining a certain width to each item from the second list, you could use the following to modify the styling for the submenu:

ul li ul li {
  float: none;
  display: block;
  width: 100%;
}

It will look like this:

You could also try using CSS Grid or CSS Flex to accomplish the structure.