sidebar on mobile under content

Hi, Yesterday evening I looked at the website toerfietsleusden.nl for the forst time on my iPad and saw that the sidebar on mobile is placed under the content area and not at the right page side. This when the iPad or iPhone is in the upright position. I change the width of the sidebar in: .sidebar-primary .widget{ width:75%; } but no result. Is there a solution for it? I cannot find one in the support forum. Kind regards Hans Hagmeijer.