Rebuild / Restructure website (maybe, using JOOMLA ?)

I built a simple website, using : PHP, HTML5, CSS and some JAVASCRIPT. The website works perfectly, as far as the back-end and functionality go (it's even gone live). However, the design is very basic (even rather "out-dated"). The outlook is old, and un-attractive, and not very user-friendly. Most importantly, the website is not FLUID. Meaning : it is not compatible with all many display devices (like : mobile devices and phones, iPads, large display screens, etc). Therefore, I need a highly-skilled WEB-DEVELOPER / WEB-DESIGNER, to perform the following tasks : (a) improve the design of my website, to make it more beautiful, attractive, and user-friendly; (b) improve the structure of the website, to make it 100% fluid and dynamic ! This means : the website should function 100% perfectly across ALL types of browsers (Chrome, IE, Mozilla, Opera, Safari).............and, ALL types of electronic devices (laptops, desktops, mobile phones, iPads, tablets, projector-screens, etc, etc). Some people use CMS tools (like Wordpress and Joomla) to build fluid and dynamic websites. I have no problem with this. However, these tools have security problems. My website is an e-commerce website, which I plan to monetize. Therefore, security is VITAL !! For this reason, Wordpress and Joomla are not very reliable. I would much prefer that : the above 2 tasks were done with PHP and CSS, and HTML. However, if a CMS tool is necessary, then I choose JOOMLA (not Wordpress !!!) (c) If Joomla will be used, please note : as I said earlier, the website already exists. I understand that the structure needs to be changed (of course). But, I do not want the CONTENT to be changed. I will provide all texts, photos and logos. (d) The website itself is small (only about 25 pages). CONDITIONS OF ASSIGNING THE PROJECT Some freelancers here have proven to be very incompetent and unprofessional. They bid on projects, for which they are not skilled enough to handle. Several times, I have found myself assigning projects to so-called "professionals", only to have them either deliver poor-quality results, or not deliver at all !!! Therefore, BEFORE I assign the project, I require that the following be done : (1) I will give you three pages from my website. Only three pages. Your job will be to RE-DESIGN or RE-STRUCTURE these pages, to fulfill the conditions stated above. For this, I will provide you the following : (a) The source codes for these pages (b) All CSS files (c) All relevant logos and/or images files. When you have designed the pages, I will test them myself on EVERY browser...........and on every device (including mobile devices, and tablets, etc) If I am satisfied with the quality of the work, then ---- and ONLY then --- will I assign the project to you (2) FTP access to my server will be given ONLY to the freelancer to whom I assign the project. For this initial test, you won't need any FTP access to my server. Any testing you need can be done on your servers. (3) The MAXIMUM budget for this job is 250 USD !