Improve website display on tablet format and portable

I have a merchant site joomla 3 My product articles are always displayed in the same way, see the examples below [login to view URL] [login to view URL] [login to view URL] On a tablet or portable format the presentation changes (see attachments): The grey block passes below the image and the space under the grey block grows a lot. I would like to improve the presentation of all "product articles" (= joomla articles) for tablet or portable formats. I would like that on the tablets and portable formats, the image appears centered and that the grey block be displayed centered . I also want the white space under the grey block to be reduced.