Convert HTML site to wordpress

I need to convert a static HTML based site to WordPress. You will need to create custom CSS files so new pages I create match the existing site. Much of the content is going to change, so this project is to create the new pages in offline mode. That is phase 1.

A second project will be to move some of the content to the new WP site. A future Phase 2.

Phase 3 will be to replace the existing site with the new WP site.