I think watching this video should pretty much explain it all. One side has position sticky, while the other side scrolls from top to bottom normally. Let me know if that helped.
Slider is quite trending feature on websites nowadays, It helps user’s to navigate easily. If you are working on wordpress it’s easy to do by using plugins.
But if your website is coding based then you have to work with HTML, CSS, JAVASCRIPT. For you can take reference from this post :- How To Create an On Scroll Fixed Header