hello, i have review your system and i worked on many portals where i have integrated amazon, ebay API and payment gateway API. I worked on many multi vendor ecommerce system and has more than 7 years of experience in development and consultancy. recently i deliver site like onlinehcs.com it will required 6 weeks approximately in development and include front end design, database development API integration Complete demo of the website will be provided that how to run all features.