When users add a product to the cart, they see a sliding cart window. In this window, you have an absolutely irrelevant "View Cart" button near the most important Checkout button. What is the purpose of having the "View Cart" button? What value does it bring to potential customers? They already are on the sliding cart window and it's enough.
Get rid of the View Cart button and make the Checkout button more prominent
On the sliding cart window, you have the "Special instructions for seller" section that takes quite a lot of space. You are selling quite simple products (clothing) where I believe the usage of that feature is close to 0%, while it takes a lot of space and catches users' attention without any value to the majority of your customers.
If it's not a must-have element needed for some purposes, get rid of that element. Instead, consider adding more relevant elements like shipping notification (i.e. Free shipping after a certain threshold, etc), upsell products, etc.
On the product page, you have a very prominent Add to Cart button. Then, on the sliding cart you are using absolutely different colors for background and the Checkout button, hence don't maintain consistency in the design of CTA-buttons in the conversion funnel. It makes the UX more complicated for shoppers. Also, the Checkout button is not really prominent and eye-catching, but it should be.
Change the background color of the sliding cart window, so you will use the same background-color for the main CTA-buttons across the funnel (ATC button, Checkout button, other buttons in the funnel). Make the Checkout button more prominent, so it will stand out among all the elements on the screen.
I hope you will find these recommendations insightful and will check your store if you don't have similar problems
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