Background color conflicts with text fields and the link color in menu

Site URL: https://julehjaelpen.dk/

Hello

I've been trying to edit the background color of the website Julehjælpen.dk. I have tried several times to come around this background color. But every new section or site I add, are always with black background. When I am trying to add sections from templates in Squarespace, the text fields are also black. They should just be white. 

But when I select a white background, the mobile menu disappears because my links in the header are white.
I would appreciate if someone could help me.

Thank you very much.

Try checking in Home > Design > Colors > Edit Theme Default > Section Background/Text...

If I change Section Background into white, the background at the menu in mobile view also turns white - and then the links are not visible. 
Is there any way to get around this? 

Header text/link use page first section color.

I am not sure that I understand. Where can I edit this?
Just to be sure, I would like the header  section to be transparent and links white. Mobile black background and white links.

Hello
When I change the background color to white, mobile background also changes into white. Hope you can help me?
 

To change mobile nav links color on only Mobile, add this to Home > Design > Custom CSS

@media screen and (max-width:767px) {
nav.header-menu-nav-list * {
    color: black;
}
}

Thanks. But now the background in drop down menu also turned white. Then the links are not readable. 
Following code can't change the background into black

.header-announcement-bar-wrapper { 
background-color: #000000!important;
  }
 

What is the name of the drop down menu, so I can change the background it in the code?
Hope you can help because the white links are not readable.

2 minutes ago, Brahe said:

What is the name of the drop down menu, so I can change the background it in the code?
Hope you can help because the white links are not readable.

.header-nav-folder-content {
    background: black !important;
}

Thank you so much

Only the links without drop down menu are black on mobile nav. Other links are still white. How can I change that?

3 hours ago, Brahe said:

Only the links without drop down menu are black on mobile nav. Other links are still white. How can I change that?

@media screen and (max-width:767px) {
nav.header-menu-nav-list * {
    color: black !important;
}
}

Thank you!