To understand Media Query Bubbling you should first have an understanding of CSS naming methodologies and Modular CSS. Here are some useful resources to get up to speed.
http://thesassway.com/advanced/modular-css-an-example Here is a comprehensive and well written example of what Modular CSS is and how to apply it in a real-world scenario.
CSS naming methodologies
http://www.hongkiat.com/blog/css-writing-methodologies To discover what CSS methodologies are and see examples of the different methods that exist, look here. I personally prefer the BEM methodology but work with whatever makes sense to you.
Writing tidy CSS
https://csswizardry.com/2017/05/writing-tidy-code For some general tips on writing clean and tidy CSS, read this article by CSS Wizardry, which has many great tips.