I don’t have a site with lessons, but I’m already working on a new blogpost about CSS Grid (this time about responsive layouts with Grid).
However, there are lots of places with awesome tutorials about CSS Grid. I highly recommend Grid by Example and also the Complete Guide to CSS Grid by CSS Tricks (which has a compilation of the Grid css properties and values). Hope it helps!
(Btw, absolutely love the Scruffy_Dog username 😊!)