Avoid having your visitors leave your website because the navigation bar is too far to scroll to. The dynamic navigation bar is a feature your customers are already familiar with because it's used in apps like Facebook and Instagram. As a visitor on your website scrolls down, the navigation bar is hidden away so they can have a full screen view of the content they are scrolling through. Then, if they want to go to the menu bar, after just scroll up a fraction it will reappear.
By adding simple features like this to your store that your visitors are already familiar with, you make a massive difference to the user's experience and as a result, they are more likely to stay on your website and see more.