Hi @lenci and welcome. I will give you principle idea how to achieve this structure.
You need one container div with height: 100vh and set it as display: flex. Inside create another 2 div’s and set their flex base width, height: 100% and overflow: scroll then add your content. Be aware that your example site has displayed images on right side that is initiated by click on left side. there is s simple trick how to achieve it and you can find ‘how to’ here on forum as for example this article. But this is on hover interaction, for click you will need as a bit different approach.
Hope that was useful info and you will be able to create it.
Good luck