How do I start troubleshooting?

[TheGabeMan]

I cloned this project, started changing things around and it already looks quite good, but there are some things I just can't change no matter what I change. So I thought for all the CSS stuff I open the page in chrome developer mode, but it is all javascripts being called what I see. So I can't seem to figure out which CSS property does what.

Few questions:

• Any tips on how to make troubleshooting or searching for the correct property easier?
• the dasboard's first line is: button_card_templates: !include_dir_merge_named button_card_templates. Will change in that file or in all the other files, be reflected immediately after a browser refresh or do (some) changes need a HA reload?
• and my actual problem, but I didn't want to post that as question since I want to learn how to face the next problem as well..... Is there a way to make the spaces between all components smaller in below screenshot, especially under the "woonkamer airco" row? Been playing with a lot of padding values, but seldom do I see a response in the page.