Sidebar smaller

Hi, The site’s url is Hagmeijer.nl As you can see there are two parts: one content part and one sidebar part. The sidebar contains text widgets. We should make some columns about different subjects in the sidebar. We should like to have a smeller sidebar, so the content are can be wider. I tried a number of solutions from the support pages, but nothing works. Problably I did not search deep enough. Is there a solution for this “problem”? Kind regards Hans Hagmeijer