Want to further improve UI and marketing messaging of website

I need a Development/UI/UX/Marketing company to help me optimize the website to convert more visitors into users and improve the look of the overall website. I had one company create the Adobe documents which had the entire UI/UX as well as the html for the website. Another company created the functionality for the site. At this point, it could look a little better, the marketing messaging could be more effective, to create explosive growth. I need all users that are being brought in through various sources, to love the site, and want to use it frequently for their (teachers) video course creation as well as for (students visiting to) learn. [login to view URL] a user generated online learning platform meant to shorten videos and make categories more specific so it is easier to find specific advanced learning content. Non traditional K-12 and screencast topics, we focus on more hands on everyday topics one encounters in life or in work. Budget target $400