how to scale background-image proportionally with container in CSS with - html

Question

for a small codeing project in codehs.com I have separate containers some labeled image some with actual images however i cannot figure out how to scale proportionally with size of webpage
here is the code for my project:
index.html
* {
box-sizing: border-box;
}
body {
font-family: Arial;
padding: 10px;
background-image: url(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSYY0m5M4elle5s14mIhUSPJQJNXWE626vaxJfyLMp-t5aQYsuS8fDBTApBr1bvM6Yu4L4:https://files.123freevectors.com/wp-content/original/110787-dark-color-blurred-background-vector.jpg&usqp=CAU);
background-size: cover;
}
/* Header/Blog Title */
.header {
padding: 30px;
text-align: center;
background: white;
}
.header h1 {
font-size: 50px;
}
/* Style the top navigation bar */
.topnav {
overflow: hidden;
background-color: #333;
}
/* Style the topnav links */
.topnav a {
float: left;
display: block;
color: #f2f2f2;
text-align: center;
padding: 14px 16px;
text-decoration: none;
}
/* Change color on hover */
.topnav a:hover {
background-color: #ddd;
color: black;
}
/* Create two unequal columns that floats next to each other */
/* Left column */
.leftcolumn {
float: left;
width: 75%;
}
/* Right column */
.rightcolumn {
float: right;
width: 25%;
padding-left: 20px;
}
/* Fake image */
.fakeimg {
background-color: #aaa;
width: 100%;
padding: 20px;
}
#first3dp {
background-image: url("https://i.all3dp.com/wp-content/uploads/2021/01/21134921/Lead.jpg");
background-size: cover;
}
/* Add a card effect for articles */
.card {
background-color: white;
padding: 20px;
margin-top: 20px;
}
/* Clear floats after the columns */
.row:after {
content: "";
display: table;
clear: both;
}
/* Footer */
.footer {
padding: 20px;
text-align: center;
background: #ddd;
margin-top: 20px;
}
/* Responsive layout - when the screen is less than 800px wide, make the two columns stack on top of each other instead of next to each other */
#media screen and (max-width: 800px) {
.leftcolumn,
.rightcolumn {
width: 100%;
padding: 0;
}
}
/* Responsive layout - when the screen is less than 400px wide, make the navigation links stack on top of each other instead of next to each other */
#media screen and (max-width: 400px) {
.topnav a {
float: none;
width: 100%;
}
}
<div class="header">
<img src="https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSzbKAzXZFQY6Sf3Jkfh_f8XPYJSMt1vHb5ZYCj4IjghC6Ue-cKiUAg78vx09asJCYmiw:https://www.fbla-pbl.org/media/2022/09/FBLA_HorizontalLogo_cropped-01.png&usqp=CAU">
<h1>Alex's 3D Printing Journey</h1>
<p></p>
</div>
<div class="topnav">
Link
Link
Link
Contact me
</div>
<div class="row">
<div class="leftcolumn">
<div class="card">
<h2>Where it started!</h2>
<h5>sometime, 2020</h5>
<div class="fakeimg" id="first3dp" style="height:200px;"> </div>
<p>Some text..</p>
<p></p>
</div>
<!--<img src="https://i.all3dp.com/wp-content/uploads/2021/01/21134921/Lead.jpg"> -->
<div class="card">
<h2>TITLE HEADING</h2>
<h5>Title description, Sep 2, 2022</h5>
<div class="fakeimg" style="height:200px;">Image</div>
<p>Some text..</p>
<p></p>
</div>
</div>
<div class="rightcolumn">
<div class="card">
<h2>About Us</h2>
<div class="fakeimg" style="height:100px;">Image</div>
<p>text...</p>
</div>
<div class="card">
<h3>Popular Post</h3>
<div class="fakeimg">
<p>Image</p>
</div>
<div class="fakeimg">
<p>Image</p>
</div>
<div class="fakeimg">
<p>Image</p>
</div>
</div>
<div class="card">
<h3>Follow Us</h3>
<p>Some text.. can use embed with social media links</p>
</div>
</div>
</div>
<div class="footer">
<h2>Footer</h2>
<h2>Footer to include credits to website creators and copyright information</h2>
</div>
use of background-size: cover;
in the id #first3dp on style.css however it did fit it to the container it did not scale proportionally with the container rather resizing the image kicking it off screen

Answer 1

your need to add the background-position property is you want a specific position when using background images in CSS.. add this code I also fixed your header which was overflowing.
.header > *{
width: 100%;
}
#first3dp {
background-image: url("https://i.all3dp.com/wp-content/uploads/2021/01/21134921/Lead.jpg");
background-size: 100% 100%;
}

Answer 2

On the header img use max-width: 100%;