Pop your store link over to me and I would be happy to check out your shop and offer any feedback I can suggest!
Thanks for sharing the link to your shop, I really enjoyed taking a look around, you have some beautiful products. I do not see the more button you are referring to that confused your customer, can you send me a screenshot of this? In regards to changing the colour of your Add to cart button, you can do this in your admin under Online store>Themes>Customize>Theme Settings>Colors:
The product recommendations that are displayed in the section are based on products that are commonly purchased together or products in related collections. Product recommendations become more accurate over time as more order and product information becomes available. You can learn more about product recommendations in our guide here, and more about the data use for product recommendations in our developer guide here.
I hope this information helps you out moving forward, feel free to reach back to me with any further information or questions and I will be happy to help out!