Intro Section with Dropdown Navigation using Flexbox and vanilla JS

I found it difficult to implement animations for the dropdown menus, so if anyone can provide any useful resources on how to do this it would be much appreciated.

I also feel that my method of handling the event listeners for the dropdown menus in the JS script is quite poor, so I would love some feedback on how I have handled it, and I would also like to learn the best methods of implementing dropdown menus.

Thanks.