imporove.existing eShop for perfumes

I'm looking for someone to help improve the functionality of my existing eShop for perfumes. Specifically, I need help with improving payment processing for transactions. I'm not looking for a complete overhaul, rather, I need improvements made to the existing setup. As such, I need someone with the technical know how and experience to fix the existing process. The ideal freelancer should be very proficient in coding, development and payment processing systems. I expect the highest level of quality and will closely monitor progress to ensure the project is completed satisfactorily and as quickly as possible.