Baskerville theme – header color and image

Hi,

I installed the Baskerville theme and I am trying to customise it. I changed the image but I noticed that there was a layer of grey above it. By searching in the posts I found that I had to add the code:
.header .cover { background-color: white; }

I did it and now my header is completely white and the image doesn’t appear anymore. So I tried to go into the files of my theme and replace header.jpg by my image header.png, I changed the name in the header.php

But I still only have a white header.

Also it took more than 5 minutes from the moment I changed the code to the moment I actually see the result online. I am wondering why isn’t it instant? I am using the “editor” mode in the admin interface of wordpress and I am doing it on a child theme of Baskerville I created myself.

I also want to customise the color of the menu, and put a texture pattern to the general background. I am having a hard time to find the right pieces of code everytime, is there something that can help me doing it?

Thanks a lot for your help!