How do I move a header banner up?

I have checked & tried every answer to earlier similar questions, but I can’t get the header banner up on the site I so willingly accepted to update: https://www.kinderenkiezenniet.nl It’s the green&blue rounds top right, obviously.

Previously the site was altered by a willing woman who figured working in stylesheet.css couldn’t be much harder than editing a Word document. I (nor she) got any clue what has been changed. This is the code in css:

[please read the forum guidelines for posting code]

div#header_banner{
width: 672px;
height: 416px;
position: absolute;
margin-left: 250px;
padding-left: 0px;
padding-top: -20px;
background-image: url('https://kinderenkiezenniet.nl/wp-content/uploads/2012/07/Circles-copy.png');
background-repeat: no-repeat;
}

div#header_banner_clickable {
width: 459;
height: 294px;
position:relative;
top:0px;
}

Any suggestions will be highly appreciated!