Magento ecommerce shop monthly maintenance - repost

Looking for a Magento and possibly a prestashop specialist for the general maintaining of a responsive eCommerce shop on a monthly basis. Task include: maintenance of product/category pages, the review of technical elements of site, customise error page - for search errors and to give a better or direct visitors to alternative search options, coding, embedding of code in relevant pages as of when needed, setting up and maintaining of landing page for newsletter subscription, design and or re-structure existing product/categories landing page and other landing pages, changing of site colour scheme as of when needed, from time to time check usability and functionality of site, etc. Ideally we would like to find someone long term who can work with us on more exciting projects due to launch in the near future.