Answer 1

Kevin Brian Official hello,
Don't you have a drawing or something relative to what you'd like to achieve to share here?
Maybe you could start with catching some tutorials about UX and UI.
Apart from that in HTML, you have some elements which help understand the purpose of each part as: <section>,<header>,<nav>,<article>,<aside>,<footer>...
Those are block level elements but it's up to you how to handle them and the content inside and for that in CSS you'll have choices with learning: positioning (static,fixed,relative,absolute),display (flexbox,grid) and other stuff...