Build a Wordpress copy of existing website

We have an existing website, [login to view URL], which is built in a custom-made CMS and it has errors. We want to switch to Wordpress. We need to export all existing data from current site (MySQL and images), make an identical copy of the front end but in Wordpress, and import all the site's data to the new WP CMS. No other changes required. The idea is that the client can manage all their exisiting and future properties in Wordpress instead of the current CMS. All properties must be added properly, as custom-post-types, and the images, texts in the three languages (EN, ES, DE), features, etc, must be added easily by client using the custom-post-types and custom-fields, not a WYSIWYG editor. Just check or uncheck boxes, and fill in text inputs and text areas, similar to existing CMS (see images), but in Wordpress. Front end must be structured like existing front end, with some static pages and the rest are CPTs / Taxonomy. The search field must work for detailed searches. - I can provide all existing files of site's PHP, CSS, JS, for both front end and back end. - The current site is in production. The switch has to be as seamless as possible from the old system to the new system. - It would help is URLs could remain the same (this is possible with WP permalinks and we have the current URLs in current DB, MySQL) on new site VS old site. If you don't understand something, ASK ME! I speak perfect English and Spanish, which are two of the site's languages, so these languages help if we can communicate better. This is a very low budget project. We're only making this change to fix errors in the CMS by swtiching to Wordpress. Thank you.