Website Design and Development - Portal -- 2

A new website (portal) needs to be designed and developed with good user experience. The portal must allow the admin to dynamically manage the content. The website must be responsive and allows the user to use in respective mobile [iOS/android] devices. Multiple users [broadly categorized into 5 types] can login and access the information - all user information need to be stored and retrieved as appropriate [Cloud integration capability to drift away from local DB or potentially get connected to cloud from day 1]. Website would need payment integration capability. Must be high on SEO - easily crawlable with no breakage links.
Mail/SMS Integration capability.