Joomla SH404sef configuration for small website

I currently have small 40 page Joomla website that has SH404sef (not used at present) and I would like the urls to be more specific as they now show the site name+category name+article name(so very long). I only want the site name + article name to show in the urls. What I am looking for is someone to make this possible either by using the sh404sef option or by simply re naming and changing the parameters of the current category and sections so they do not show up in the url as every time I try this it results in 404 errors on the already live pages.
Thanks