Refining the self-written site

Im looking for an artist who is well versed in programming (php, curl, ajax, json, javascript, html/css).
There is a website (for delivery service) written without the use of CMS. Goods, shares and other parameters are loaded on the api of their own system, returned to json and directly processed on the customers side (site).
In a nutshell, the task is to rewrite the processing of api products and some other parameters in connection with the changes in api (significantly changed the structure of json unloading goods).
The job is not only to change the settings from json to new ones, but also to add/change some of the functions of the site.
Detailed TK and access to the code are attached!