PLEASE HELP! custom css

I am working with the church theme “resurrect” and I am needing custom css help to be able to make the banner/header smaller. They have it set at a massive size and I need it to be smaller. I also need to change the text color they have on the home page logo section. These should be easy changes but they want me to setup everything in a child theme when all I need is some help with the css. Can anyone help with what I need to put into css to change these settings? Thank you!!!

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