virtual-classroom | A web application using webRTC , Websocket , node.js | Websocket library

There are many questions about this on how to animate a header into shrinking as the page scroll down. Although I have a basic idea on many responses to similar questions, my case is quite complex I believe. My header takes too much space when it's static or fixed. The full header contains a pre-header with social media links, small address and a log in button, a title-header: it has the logo image and the name of the business and motto, and finally the navigation menu. Again all of this wrapped in a div with their following sub divs. I used bootstrap as template the menu navigation. Basically what I am looking to do is when scrolling down I would like the pre-header and logo image disappear keeping just the title name, motto and navigation menu. Here's the following code.

Css code is also included in the snippet, sorry if it's too long and confusing. It contains styling of other pages of the same project. Any suggestions would be appreciated.