How to Learn CSS in 2020?

I vaguely flirted with some CSS in 2013 or so - back then I was a backend developer who sometimes dabbled in CSS. Now I want to sit down and really focus on improving my CSS, but the problem is that the internet is really filled with contradictory advice, and often much of it is outdated. For example, I'll be googling how to set up a certain kind of layout, and I'll get answers about using a (non-responsive) table layout vs flexbox or CSS grid.

Can anyone recommend a new/modern resource for picking up CSS that won't leave me with bad habits?