website design for marketplace negotiation

I am looking for a web designer to create a contemporary marketplace website with communication and negotiation tools. This website will be used to serve the needs of B2C customers, and should provide advanced search and filter options. Although I am open to suggestions, it is important that the website has a professional, modern design that enables a smooth end-user experience. The chosen design should be aesthetically pleasing, functional, and easy to navigate. Furthermore, the website development should include responsive design and mobile compatibility. Finally, the designer must ensure that the website's security meets all current industry standards.