can't change colors

I followed the directions here:

https://docs.themeisle.com/article/14-how-to-create-a-child-theme

to make a child theme. I added one rule:

.red-btn{
  background-color:#ffaf0f;
}

And it doesn’t show up at all. When I remove the code the tutorial says to add to functions.php and add this to the style.css file:

@import url("../zerif-lite/style.css");

the color does change, but all of a sudden I can’t change some other things about the theme, such as the site title and tag-line. I must be able to change both somehow, but I have no idea. The code in my functions.php file is exactly the same as that in the tutorial.