Answer 1

Search the functions that are giving you trouble and usually something pops up on google .
https://stackoverflow.com/questions/24219702/struggling-with-classlist-add-and-getelementsbyclassname

change your DropDown function to this and it should work

function DropDown() {
var elements = document.getElementsByClassName("dropdown");
for(ele of elements) {
ele.classList.toggle('active')
}
}