Hi Geraldine-
Without some more data it's difficult to pinpoint where your customers are dropping off (where the friction is), but just on a quick review a few things come to mind that might be worth testing:
- Image Carousel - There's a lot of data out there that suggests that image carousels / sliders hinder conversions. In your case on the home page it's going way to fast and has a lot of text on it, making it almost impossible to read (and I read fast :). Consider a static element that more clearly articulates your benefits, conveys trust, etc (and don't feel like you have to jam every piece of information in there).
- There's a lot going on in your design, including products, categories, newsletter, affiliates, etc. Consider going through each page and asking yourself - where do we want the visitors (or segments within) to go, how do we get them to the products that they're interested in, and how can we eliminate distractions from that path?
- The modal window that pops up after "add to cart" is a bit strange. I think the user experience there could be improved by an animation closer to or on that button, and I'm not sure how well that works for mobile.
- The checkout page might be daunting. Consider splitting up or progressively revealing the forms so the user doesn't get overwhelmed.
- Consider replacing the text input for the discount code with a link that then reveals it. Showing it by default may dissuade visitors that don't have a code (because they think they're not getting the best deal).
- It may be worth trying Shipping Address instead of Billing Address as the first step (and change the checkbox below accordingly). With Shipping I feel like I'm getting something vs giving you something (Billing)
- Finally - do you have a problem with abandonment? Might be worth looking into techniques like cart recovery, exit intent and / or retargeting if so.
As I mentioned just some initial thoughts without looking at data, and these are just ideas that warrant testing. Hope this helps.
Arun