Fix and improve the functionality of the website on Wordpress

It is necessary to fix and improve the functionality of the website on Wordpress (php, ajax, js, jQuery, mysql) Site theme: online exchange, e-commerce. This requires a specialist in PHP and web programming. The level of tasks is average and above average, most of them are backend. You also need to know and use Github.
Interested in long-term cooperation.
Level of training - Senior Developer, experience 8-10 years.
Please respond with a description of your training, experience, and pricing.
The address of the site and the details of the tasks will be provided to candidates with the appropriate skills upon request.