I want to switch from main (home) section to, for instance, about section. I want to just replace my main content with new about section (whole bootstrap container). I want to make it fade out while about section comes in. Of course, without refreshing the page. Like on this website (try switching sections): https://covid19stats.live/
How can I do it?
I am not sure what you really want..
but normally you place your content in different .html files and refer to them with a button or a link:
<a href="about.html"
title="more informations">
Href-attribute
</a>
edit: if you want to just change the content you need to use Ajax