Can I copy all code in custom.css or only code that I changed?

Hello,
I would copy only the code you changed. Otherwise its 5000 line of code and it gets a mess

If I click on Customizer, Is only theme.css or even headerbar restored?
Because now I see the img background also from mobile.
If I apply the customizer, it becomes a black background and with custom.css I can’t restore it frome code in theme.css.

Can I add a white bar up of headerbar background and move down this img? Only for mobile!

I fixed it.
I created a theme.css before and a theme.css after the Customizer. I changed the values to px and it worked.

One last question: the logo is in too low position in ipad display (width = 1024px), compared to the gray bar. Can I turn it up a bit, just for the iPad? From 500px to 1154px. Thanks a lot

Problem solved.