Carrington header problems

I’m having three problems:

1. I upload images of various sizes as a header on Carrington, but a gray background always remains.

2. How do I move the location of the blog title in the header?

3. Is there a way to get rid of “categories” in the subheader, and instead move the different page links to that subheader?

Any help would be much appreciated. If you want to look at my blog to see what I’m talking about, it’s https://www.shelbygrossman.com

Many thanks,

Shelby