Hello,

so I am a WordPress beginner and I'm doing my first site. I have a page with Astra theme, Starter template plugin, and free Elementor builder. I made some changes on the header - via Customize -> Additional CSS) that are clearly visible on big screen/big resolution. As soon as I change to tablet or mobile the CSS that I added doesn't work. I want to change the breaking point and make the website more responsive, but because for some reason my additional CSS doesn't work on mobile, I can't get my media queries inside the additional CSS to work either, and the styles that I made for desktop aren't visible on mobile.
Now I thought that I can take a look at the CSS files under Appearance -> Theme settings, but there are so many CSS files there and so many repeating media queries that I can't make sense of it, to where I should add my custom queries or my custom style to an element.
So my question is, how can I make additional CSS to work on the mobile version, or/and how and where do you add your own media queries to change the breaking points and do additional styling?
How to find what CSS file the theme uses for making those changes?

Thank you for your help