How to modify media querys on a concept

Hello,

so I am a WordPress starter and I’m undertaking my 1st web page. I have a web page with Astra topic, Starter template plugin, and totally free Elementor builder. I made some adjustments on the header – through Customize -> More CSS) that are obviously noticeable on significant monitor/large resolution. As before long as I alter to tablet or cell the CSS that I additional would not work. I want to transform the breaking stage and make the site much more responsive, but due to the fact for some explanation my additional CSS doesn’t function on mobile, I are not able to get my media queries inside the extra CSS to work possibly, and the variations that I manufactured for desktop aren’t seen on cell.
Now I believed that I can choose a seem at the CSS information less than Visual appearance -> Concept options, but there are so lots of CSS information there and so several repeating media queries that I are unable to make feeling of it, to where by I must add my customized queries or my personalized design and style to an element.
So my query is, how can I make further CSS to get the job done on the mobile variation, or/and how and the place do you include your possess media queries to alter the breaking details and do more styling?
How to come across what CSS file the theme makes use of for making these modifications?

Thank you for your help