Mobile vs laptop issues

Hi,

I’ve just made som small adjustments to the header (menu colors and tagline colors).

These adjustments doesn’t seem to work on the mobile. I have an iPhone.

Go to rsrdesign.dk and see the difference both on mobile and laptop

On the laptop the tagline is white/mobile darkgrey and the menu color on laptop is white/”invisible” on mobile. I know this is because of the white background on the mobile.

Any solutions anyone? Thank you so much for taking your time helping out a newbie! ??