На самом деле из вашего объяснения и изображений я понимаю, что вы хотите разделить свою страницу на две разные области:
- контейнер истории с несколькими столбцами
- область уведомлений с одним столбцом
В отличие от текущего основного контейнера с тремя столбцами, который у вас есть сейчас.
Без использования Flexbox и CSS -grid я создал фрагмент с тем, что, как я понимаю, вы хотите. Я добавил несколько дополнительных статей и фоновые цвета, чтобы показать структуру, и прокомментировал CSS, где это возможно ...
Бонус: добавил некоторое «отзывчивое» поведение с использованием как математических, так и @media запросов.
/* Generally accepted preferred rules */
html,body { box-sizing: border-box; width: 100%; max-width: 100%; height: 100% }
*::before,*::after, * { box-sizing: inherit }
/* remove some default HTML spacing (when required, use padding instead) */
body,h1,h2,h3,h4,h5,h6,p { margin: 0 }
/* define page structure */
.main { height: 100%; width: 100% } /* avoid using <main> */
/* mobile first, 1 column */
section { max-width: 67%; float: left; column-count: 1; column-gap: 1.25rem }
aside { max-width: calc(33% - 1.25rem); float: right } /* minus column-gap */
article { break-inside: avoid } /* keeps content in the same column */
/* some responsiveness */
@media (min-width: 961px) { section { column-count: 2 } }
@media (min-width: 1281px) { section { column-count: 3 } }
/*
responsive page padding (linear equation y = mx + b)
p1(320,32) p2(1920, 72) => 0.025x + 24
p3(320, 8) p4(1920,320) => 0.195x - 54.4
grow from 32px on a 320px viewport to 72px on a 1920px viewport
grow from 8px on a 320px viewport to 320px on a 1920px viewport
*/
.padded {
padding: calc( 2.5vh + 24px) calc(19.5vw - 54.4px)
}
/* eye-candy only */
header {
column-span: all; /* span full container */
padding: 1.25rem; /* equal to column-gap */
background-color: Black; Color: White;
}
h1 { line-height: 1.25rem }
h2,p { padding-bottom: .5em }
section>article { background-color: Beige }
aside>article { background-color: rgba(0,0,0,.1); color: Black }
article {
padding: 1.25rem; /* equal to column-gap */
margin-bottom: 0.5rem /* space between articles */
}
[outlines="1"] * { outline: 1px dotted }
<div class="main padded" outlines="0">
<section>
<header>
<h1>Welkom op Het bedrijf</h1>
</header>
<article>
<h2>Story 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
</article>
<article>
<h2>Story 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
</article>
<article>
<h2>Story 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
</article>
<article>
<h2>Story 4</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
</article>
<article>
<h2>Story 5</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum interdum,
egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenaseget maximus sem, in volutpat est.</p>
</article>
</section>
<aside>
<header>
<h1>What's new?</h1>
</header>
<article>
<h2>What's new 1</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum
interdum, egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenas eget maximus sem, in
volutpat est.</p>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum
interdum, egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenas eget maximus sem, in
volutpat est.</p>
</article>
<article>
<h2>What's new 2</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum
interdum, egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenas eget maximus sem, in
volutpat est.</p>
</article>
<article>
<h2>What's new 3</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque euismod ex vel lobortis molestie. Pellentesque a ipsum
interdum, egestas enim in, rutrum justo. Phasellus dictum luctus sem, at blandit diam tempor sed. Maecenas eget maximus sem, in
volutpat est.</p>
</article>
</aside>
</div>