I would suggest you to integrate a "Sticky Add to Cart" option on product page and a "Sticky Proceed to Checkout" too on cart page? In some of our product, the description is longer than normal and customers sometimes have to scroll back all the way up to see the Add to cart again which can get them frustrated. It's could be a good thing to have a sticky add to cart appearing at the bottom of the product page either on desktop and mobile when customers, because they scroll down, don't see the regular add to cart button anymore.

The "Sticky Proceed to Checkout" on the cart page would be useful to get customers clicking to go to the checkout page before getting distracted.