Integrate an existing website into wordpress theme

This is part of a larger project to overhaul an old website into a new CMS using WordPress. There are other parts of this project that will be available at later stage to successful candidate. Objective: Integrate an existing site build on PHP/Apache with no CMS (screenshot) into WordPress site with a theme and modern navigation menu using sliders similar to GilidPanel - The existing code must integrate within WordPress (The current site is NOT wordpress, its custom mix of HTML/PHTML/PHP). There are approximately 36 PHP pages to integrate within the new theme 1) Unify the login where WordPress Login uses the existing database for authentication. Usually done using "External Database Authentication Reloaded" Plugin for WP. 2) Install a theme (we will purchase it and provide one) and integrate the existing /admin/ section of the website into that theme 3) Install Slider Navigation, and setup Menus as requested (About 10 menus when fully extended) Developer Requirement: - Must have STRONG experience with WordPress. - Have successfully integrated existing websites into wordpress - Confidentiality Agreement is required - Medium to Excellent knowledge in PHP and MySQL - Excellent HTML/JS knowledge - Familiar and good working level with Linux Shell, SSH. The Environment: - Existing website is a sub-folder /admin/ of a website. We just need the /admin/ to be imported into wordpress as a proof of concept - It is running on PHP 5.4 , pgSQL, Apache 2 - We will be providing remote MySQL server v5.6 for WordPress - No GUI, phpPgAdmin is available and so is phpMyAdmin, however, this is command line environment ** To be considered for this project, you must answer the questions below **: - Have you integrated an existing website into WordPress? - How much time do you anticipate (roughly) such project will take to complete? - What problem do you foresee in this project? ==== The site structure is: /admin/ /app/ |_ /views |_ /admin Description of attache files: [login to view URL] : This is a sample screenshot of /admin/[login to view URL] loading (there is a login screen prior to seeing this page) [login to view URL] : is the main [login to view URL] file (it is PHP, not .html), and it loads various other files. This file is located in /admin/[login to view URL] [login to view URL]: is one of the files called by [login to view URL] and is located inside /app/views/admin/ , it is the one that calls footers, headers, JS and CSS files The other files are PHTML that are referenced by [login to view URL] What likely we need to do is integrate the [login to view URL], [login to view URL] in a way within wordpress and have the themes apply there. If you require further information, please ask. I am also open to creating a theme without integrating with WordPress, the goal is to change the look&feel of the /admin/ section, please specify which option are you proposing.