Product-Landing-Page- Feedback. I am very disappointed in myself

Tell us what’s happening:
I am really disappointed in myself. I have spent quite a bit of time to get this product landing page right.
The more I work it messier it is gets. At the end I don’t really know what is going on.
I tried to copy FCC sample but still messed it up.
I am not sure how to break it down the project to smaller pieces so it does not mess up entire page once I change font or width.
Which elements needs to be styled first, which properties necessary or unnecessary and which one goes first or second. Ughghghg
It seems like big giant puzzle except it has own gazillion puzzles, which has gazillion ways to approach…
I have finished HTML/CSS. and Javascript Algorithms And Data Structures Certification. I liked solving coding algorithm challenges. But HTML/CSS projects makes me think maybe this is not my thing. I have spent lots of time to this point but I really want to give up all of it.
Sorry for the rant. I am sure there are people have/had this. Maybe you can share your struggles.
Your code so far


"use strict";
import subtract from "math_funcions";
subtract(7,4);

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36.

Link to the challenge: