Changes in Shopify "Debut" Theme on product page and shopping cart page

I'm currently setting up my Shopify Online Shop and due to the "small business regulation" in Germany I need help in applying few small changes to the product and shopping cart page. More details are described in the ppt file attached. In addition, I need to know how I can put these changes back to the original, because this is required once I exceed a certain revenue limit with my store in the future.