How to remove/hide the number of products under the category list?

Try this CSS

.header-categories ul li :not(a) {
    color: white;
}

Thank you so much, It perfectly worked for me.

Can you please also help me with,

How to hide subcategory and show when hovering over the main category in the drop-down category? For reference, please check out the screenshot https://imgur.com/a/5gfLJg0

Thanks & Best Regards,

Try this, I think it may work

.header-categories .cat-item ul {
    display: none;
}
.header-categories .cat-item:hover ul {
    display: block;
}

Thank You So much again, It worked for me.