What do I need to learn?

Hi I havent made a website for some years. I master html/css and some javascript. What would i need to learn in order to make a flatfile site in Grav?

Hi, Grav is based on a collection of technologies pretty well described on this Learn site page.

But at the end of the day, you're still writing HTML and CSS, just in a way that allows Grav to fill the templates with data, so if you already know those, you're already 50% done.