Catergories mobile/desktop

Hi I use this code currently to stack catergories on mobile but I still dont like how it looks. Is it possible to make a drop down box with the list or catergories and seperate the catergories from the 'collections' and also a drop down on desktop view also? Or any suggestion to make it better please?

/* Show category nav links */
div.nested-category-tree-wrapper {
    display: flex !important;
    float: none !important;
    min-width: 100% !important;
    max-width: 100% !important;
    margin-right: 0 !important;
}
section.products.collection-content-wrapper.products-list {
    flex-direction: column !important;
    display: flex;
}
.nested-category-tree-wrapper>ul {
    width: 100% !important;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}
.nested-category-tree-wrapper>ul li {
    margin-left: 2vw;
}
nav.nested-category-breadcrumb {
    display: none !important;
}
ul.nested-category-children {
    display: none !important;
}
li.category-item:first-child a {
    padding-bottom: 0 !important;
}
 

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