sorry for bad english. Any ideas to move this onto the center without using margins etc.? Maybe there are other ways.

And is it possible for the image and video to auto adjust on any mobile screens? Below the code I used:
HTML
<div id="tv_container">
<iframe width="720" height="480" src="https://www.youtube.com/embed/vToBbWibGw8?controls=0" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
</div>
CSS
#tv_container {
width: 720px;
height: 480px;
position: relative;
}
#tv_container:after { //frame
content: '';
display: block;
background: url('../home-img/framevid(4).png') no-repeat top left transparent;
width: 100%;
height: 100%;
left: 0px;
top: 0px;
position: absolute;
z-index: 10;
}
#tv_container iframe { //video
position: absolute;
top: 30px;
left: 40px;
z-index: 5;
}
Use text-align: center to your object style.
I don't know which objects you want to centered but it should works with all of them.
I just added CSS and HTML elements through JS. Here is my code:
#tv_container {
width: 720px;
height: 480px;
position: relative;
}
#tv_container:after {
content: '';
display: block;
background: url('../home-img/framevid(4).png') no-repeat top left transparent;
width: 100%;
height: 100%;
left: 0px;
top: 0px;
position: absolute;
z-index: 10;
}
#tv_container iframe {
position: absolute;
top: 30px;
left: 40px;
z-index: 5;
}
.frame {
display: flex;
justify-content: center;
}
<body>
<section class="frame">
<div id="tv_container">
<iframe width="720" height="480" src="https://www.youtube.com/embed/vToBbWibGw8?controls=0" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
</div>
</section>
</body>
You can use 3 ways to center the image:
margin: 0px auto;
display: flex;
justify-content: center;
// justify-self: center;
// justify-items: center;
// align-items: center;
// ...
As for the size of the image in different page sizes, I must say that setting the width of the page should not be using pixels and you should use the percentage as follows:
width: 80%;