Built with html, css, javascript

Hello guys here is solution for my Intro section with drop down navigation, i have being working on this project for a while now and still wasn't able to complete it. I was able to do the css styling and page layout for desktop and larger devices but i wasnt able to to toggle the navigation for mobile and smaller devices. The only section i was't able to complete is the navigation bar. Any tips on how to fix this or improve my code, will really appreciate it.