Convert a website to be "responsive"

DO NOT APPLY FOR THIS PROJECT UNLESS YOU HAVE EXTENSIVE CSS SKILLS AND EXPERIENCE CREATING RESPONSIVE WEBSITES. I WILL ASK TO SEE EXAMPLES OF RESPONSIVE WEBSITES YOU HAVE CREATED. I need to get the website [login to view URL] converted to be "responsive", meaning it needs to display a different layout/content based on the browser's platform and/or dimensions. The website was developed using a custom CMS (NOT WordPress, Joomla, etc). I have full control over the HTML generated by the CMS, and need someone to change the CSS to make the website responsive. No changes are required to the website's appearance when viewed in a desktop browser. The fewer changes to the underlying HTML, the better. I am hoping for a CSS-only solution (if possible). I am a website developer with excellent back-end skills (PHP, MySQL etc), but my CSS skills are not sufficient to make the website responsive. I am the developer of this website, but not the owner. DETAILS When viewed on a mobile phone, the home page should be just the left hand section of the current website starting with the logo on top with a phone icon (that links to the Contact page). Underneath that, we need the "Book Now" section down to "Recent Tweets". The rest of the homepage content can be skipped if viewed on a mobile phone. If the visitor clicks on a link to a trip, then we just need: • The trip title • The first photo • The Booking Box with the departures • The YouTube link (if there is one) • The names of the highlights or days of the itinerary. If they click on this then it expands to show the detailed description. • Inclusions • Pick up points What is not required from the trip page: • More than one photo • The text i.e. trip description, details of the highlights or itinerary days • Any attached PDFs The booking page and the checkout page need similar treatment.