The most important things to learn as a beginner using Chrome Developer Tools, and a little info on Device Mode.
1.) Chrome Dev Tools are awesome, and the more you can dive in and try to use them, the faster your skill level will grow.
2.) Use the documentation, even if you’ve never read documentation before. https://developers.google.com/web/tools/chrome-devtools/
3.) Once you start to get comfortable in one tab, stretch yourself. Working effectively with all of the tabs will serve you exponentially more than sticking in your comfort zone.