Answer 1

Simple. Move the closing bracket from line 4 onto line 10. You are closing the function start() before you need to. Also remove the var on line 7 as youve already defined Niw.

Like this;

function Start(){
var Niw = document.getElementById("Cirb");
Niw.style.color="black";

var Col = document.getElementById("Cirb");
if(Col.style.color=="black"){
Niw = document.getElementById("Lur");
Niw.style.color="black";
}
}

Answer 2

Hey there. You're trying to access the property of the div element with an id of Cirb on line 6. The problem is that the element doesn't have any color property so it's value is null.