“Collapsible Text” code not working

I want 2 insert a code 4 “collapsible text”…I mean the ones you see in a FAQ’s list. I already have the code & it’s already working as a web page. Therefore, I copied the whole source code & pasted it in the HTML view of my post editor.

This is the unsatisfactory result.
What do I do?

Below is the source code that I posted:

[Code moderated as per the Forum Rules. Please use the pastebin]

P.S: Btw, is there any other way to show huge code here other than using the “blockquote“.