Customise Burger Menu

Site URL: https://www.hastingscity.co.nz/

Hello

I have added a Burger Menu to our website and I'm not sure how to further customise it using CSS only (version 7.1 sqsp).  I really need some help if possible please!

Question 1: Does anyone know the code to add, so the text will right-align?

Question 2: Is it possible to add Headers with clickable links underneath i.e. category header then the sub-menu items? If so, what is the CSS pleeeease, have tried so many ways and nothing works. Also if those headers can be colour customised?  Like image attached but for DESKTOP

Question 3: Does anyone know the code to change the background of the pop-out burger menu so is white font on a coloured background?

Q1. Q3. Add to Design > custom CSS

@media screen and (min-width:992px) {
.header-menu-nav-folder-content * {
    text-align: right !important;
}
.header-menu-bg.theme-bg--primary {
    background: red !important;
}
.header-menu-nav-folder-content * {
    color: white !important;
}
}