responsive url shortening

My difficulties for this challenge:

I've never done a landing page, so due to lack of skill with it, I had a hard time;

I had difficulty positioning some elements.

I had A BIG DIFFICULTY for class names in CSS and variables/functions in JS. Taking advantage, if you can point me to videos, articles on these issues, I would be very grateful.

Despite the difficulties, I learned many things doing this challenge and I was very happy with the result, I thought it would be much worse.