Product Landing Page Formatting Advice

I’m having difficulty with formatting my page correctly. One thing I really don’t understand is why commands are only working when assigned to ul, li, and a as opposed to the id/class listen in the tag. Any advice as to had to go about this project would be great!

Here is the product I am trying to make a page for: http://udo-audio.com/

Here is my code: https://codepen.io/IanGoodman/pen/jOqpZjb

can you give an example of what you tried here?

I tried altering the text color, alignment, and padding using #nav-bar