Thanks for answering! I use the Custom CSS theme option exactly the way to said it: I copy bit of CSS I want to change and make the changes there. The problem was I couldn’t find the CSS to copy it from!
But I think I have fixed the issue now, I have dug around the file a bit more and I believe I found it. Thanks for pointing me in the right direction, I didn’t know themes could have multiple ones.
Thank you!