How i can create pictures box in first page?

This is my website http://www.amazingcouple.net Yesterday i buy your theme and install it to my website.

Now i have 3 problem detail as below

1. I need to know the perfect size of Header background
2. How can i change topic of 3 columns in footer?
3. How can i modify first page like your demo? I need to see the column of pictures on the top of first page like this link https://www.amazingcouple.net/category/food-review/ and I need to show more topic in first like your demo.

Best Regards,
Rod W.

Now i can solve all problem but i have a new problem that need your support.

How can i add or create sub menu beside “New Release” in first page of my website https://www.amazingcouple.net/. I need to add categories beside if for easy to read and search.

Thank you very much