Sub Menu Not auto extending

Hello, I have a problem with the sub menu I have set an additional CSS code to do the job of auto extending the submenu width when adding new items. The CSS code is
#colophon .gallery-columns-4 .gallery-item {
padding: 2px;
}
#colophon .widget_text {
margin-bottom: 0;
}
#colophon .widget, #colophon .widget_text .textwidget {
padding-bottom: 0;
}
.footer-widgets-wrapper {
border-top: 0;
}
/* disable text wrap in sub-menu */
ul.menu ul {
white-space: nowrap;
}

/* extend sub-menu width to match text */
ul.menu ul {
width: auto;
}

Can you let me know what I should change, so the sub-menu background covers all sub menu items.

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