Can I change the color of the font, change the header to an image without creating a child theme?
You can upload a logo under Settings > Website > Appearance. If you want the entire header to use a background image, you'll need to use a child theme. Generally speaking, I don't recommend it because it's very difficult to make an image look good across a range of device widths.
And in viewing the books, There is a word Array above the categories, I dunno where it came from. How can I remove it?
No idea. It looks like you have a custom block of some kind that appears just above it, so I'd check your code around that to see if there's anything stray getting printed.
The code for the categories block is under
But judging from the placement of the word, I'd say it's something that's happening before the categories block, so more likely caused by the block above it.