Add a feature to my shopify Theme this replaces the first one that has expired

Hi, We are using the Shopify theme called Brooklyn. In carrying out this task, I want to make the feature /tool: 1) look like this is not an add-on feature of the store; 2) view-able on the page you land on without having to scroll up or down at any time; and 3) look appealing to pretty much what will be, a female only audience. In essence, there are products which you can buy and the Brooklyn Shopify theme allows us to place these into product categories. I want to add a feature where people can scroll left or right through 1 category of products in the top portion of the screen (see attached this product has 1 picture in the image), and then directly below and view-able on the same screen, be able to scroll left or right in the bottom portion of the screen of another category of products (see attached this product has 2 pictures in the image). To the right of the displayed products, I need the customer to have the ability to choose with respec to each product, the size desired and after choosing the size, to be able to click on the plus (+) and minus (-) symbols to indicate how many items they wish to purchase. To the left of the product, have a banner which advertising an/or a slideshow can be displayed, or if desired be left white like the rest of the background. Finally, when a customer stops scrolling tops and bottoms, I would then like to give the customer the ability to turn the chosen top and bottom into a set and add that set to their shopping cart, noting, that any 2 products bought together gain a 10% discount. I look forward to hearing your ideas.