If you see horizontal scrollbar on your website, then it most probably was caused by some elements on website that are placed too far to the right from site content. You can easily check this. Enter website builder and check if all pages have horizontal scrollbar in the editor. If they do, then scroll right to the end and you will most probably find an element there (note that it can be absolutely white - for example small white shape - so it can sometimes be hard to detect it). Position the element properly inside content bounds or delete it if is not needed. If this element is needed only in one version (Wide, Desktop, Tablet, Phone), you can right-click it and choose to hide it in context menu.
If no such elements left on page in the editor, the horizontal scrollbar must disappear. After that publish your website.