CSS modification not applying to the project at all?

I created a website to teach blind typing. However, while running it, i noticed that none of my CSS midifications happen… I tried debugging and searching the internet for similar problems but I cannot find the problem myself and so will appreciate a second pair of eyes to look it over and help me resolve this…
Thanks in advance <3

My HTML code:

    <head>

        <title>Blind Typing</title>
        <h2> Learn how to type blindly today! </h2>
        <h4> Follow these simple exercises and become a blind typer! </h4>
        <link rel="stylesheet" href="../blindTyping.css">
        <script src="https://code.jquery.com/jquery-3.6.0.js"></script>
        <script src="../blindTyping.js"></script>

    </head>

    <body>
        
        <div>
        
            <div class="exp">
        
                Copy the following quote, without looking at the keyboard!, to the best of  you ability.
        
            </div>
            
            <div class="menu">
                
                Choose diffeculty level:
                <ul>
                    <li><button class="easy">Beginner</button></li>
                    <li><button class ="mid">Intermediate</button></li>
                    <li><button class="hard">Expert</button></li>
                </ul>
            </div>
        
            <div class="original" id="exc">
        
            </div>
            
            <div id="timer">
            
                <button class="start">start</button>
                <button class="stop">stop</button>
                <p class="timer"></p>
            
            </div>
        
            <div class="copy" id="exc">
        
                <input type="text">
                
                <p id="msg" class="oops" background-color="red"></p>
                <p  id="msg" class="success" background-color="green">Congratulation! You made it! Now go and try the next one! </p>
            
                <button class="under" id="next">Next Exercise</button>
                <button class="under" id="return">Return to Menu</button>
                
            </div>
        </div>

    </body>

</html>

My javascript code:

/*global $, document*/

var easy = ["This is a test", "This is another test"];
var med = ["This is a medium quote"];
var hard = ["This is a hard quote"];

var cntq, currIndex = 0, mistakes = 0;

$(document).ready(function () {
    "use strict";
   
    $("#exc").hide();
    $(".oops").hide();
    $(".success").hide();
    $(".stop").hide();
    
        
$(".easy").on("click", function () {
    cntq = easy;
    $("#exc").show();
    $(".menu").hide();
    $(".original").html("<p>"+easy[currIndex]+"</p>");
});
    
$(".mid").on("click", function () {
    cntq = med;
    $("#exc").show();
    $(".menu").hide();
    $(".original").html("<p>"+med[currIndex]+"</p>");
});
    
$(".hard").on("click", function () {
    cntq = hard;
    $("#exc").show();
    $(".menu").hide();
    $(".original").html("<p>"+hard[currIndex]+"</p>");
});
    
$("#next").on("click", function () {
    currIndex++;
    mistakes = 0;
});
    
$("#return").on("click", function () {
    $("#exc").hide();
    currIndex = 0;
});
    
$("input").on("input propertychange", function () {
    $(".oops").hide();
    $(".success").hide();
    var chk = $("input").val();
    var org = cntq[currIndex];
    var errorFound = false;
    var newHTML = "";
        
    // Check letter by letter if the input matches the original sentence
    for(var i=0; i<chk.length&&!errorFound;i++){
        if(chk[i]===org[i]){
            // Add mark tag to the current letter in the original text to show user progress
            newHTML = newHTML +"<mark>"+org[i]+"</mark>";            }
        else{
            // If there's a mistake, alert user and delete the input so user can try again
            newHTML = cntq[currIndex];
            mistakes++;
            errorFound = true;
        }
    }
        
    // Check if there was a mistake
    if(errorFound){
        $(".oops").text("Oops! You made " + mistakes+ " mistakes.");
    }
        
    // complete the original sentence if the input is still unfinished with the rest of the org sentence
    if(i != org.length){
        for(;i<org.length;i++){
            newHTML+=org[i];
        }
    }// Check whether the sentence matches the original completely
    else if (newHTML === org){
        $(".success").show();
    }
        
    $(".orginal").html(newHTML);
    $("mark").attr("background-color='yellow'");
});
   
function getdate(){
    var today = new Date();
    //var h = today.getHours();
    var m = today.getMinutes();
    var s = today.getSeconds();
    if(s<10){
        s = "0"+s;
    }
    if (m < 10) {
        m = "0" + m;
    }
    $(".timer").text(m+" : "+s);
    $(".start").hide();
    $(".stop").show();
    setTimeout(function(){getdate()}, 500);
}

$(".start").on("click", getdate);

$(".stop").on("click", function() {
    $(".start").show();
});
    
}); // End ready function

My CSS code:

title h2 h4 {
    left: 50%;
    transform: translate(-50%,0);
    text-align: center;
    position: absolute;
    border-radius: 5px;
    box-shadow: 0px 8px 16px 0px;
}

body {
    left: 50%;
    transform: translate(-50%,0);
    text-align: center;
    position: absolute;
    border-radius: 5px;
}

ul .menu {
    list-style-type: none;
    margin: 0;
    padding: 0;
}

li button {
    display: block;
    width: 60px;
}

mark {
  background-color: yellow;
  color: black;
}

input 
{
    display: block;
    width: 500px;
    height: 200px;
}

.under {
    display:inline-block;
}

#next {
    float: right;
    position: absolute;
}

#return {
    float: left;
    position: absolute;
}

p #msg {
    border-radius: 10px;
    padding: 20px;
    width: 500px;
    height: 50px;
}

.oops {
    border: 2px red
}

.success {
    border: 2px green;
}

#timer {
    right: 5%;
    text-align: center;
    position: absolute;
    border-radius: 5px;
    box-shadow: 0px 8px 16px 0px;
}