You should split your list in two:
@if (CurrentPage.Children.Where("Visible").Any())
{
<section class="news-list">
@* For each child page under the root node, where the property umbracoNaviHide is not True *@
@foreach (var childPage in CurrentPage.Children.Where("Visible").Where("topNews").OrderBy("CreateDate desc"))
{
<article class="news-item top-news">
<a href="@childPage.Url">@childPage.Name (Topnyhed)</a>
</article>
}
@foreach (var childPage in CurrentPage.Children.Where("Visible").Where("not topNews").OrderBy("CreateDate desc"))
{
<article class="news-item">
<a href="@childPage.Url">@childPage.Name (Topnyhed)</a>
</article>
}
</section>
}
And then wrap div around what you need.