Convert existing booking website design to responsive

Client would like their website to be responsive, but for the desktop version to remain as it is just now. The successful applicant would be required to create a main framework (header, nav, main, and footer) which would carry through to all breakpoints and be reworked according to the screen size. The site itself is database-driven, but the designer won't need to get involved with any of the data. We would supply access to the live site to let the designer see what each of the 'main' areas are for the redesign. These individual areas would be: Page display (home content, individual page content) A booking area (small form, then a larger form, then a thumbnail display with some info, then a larger product page with info, then a final form) Thumbnail display using dbase data and images Full product page with info Customer accounts area So, realistically, there is the main framework with the header, nav, main, and footer, and the content within the 'main' would only ever be one of the five areas above. The designer wouldn't need to make any changes to the actual software, only design what the software delivers, and I would then go through and write everything in to the Perl software myself.