I highly recommend Rachel Andrew and her clear explanations of the latest CSS for layouts, responsive and otherwise: https://thecssworkshop.com/
if you want a Virgil to guide you through HTML/CSS/finally setting up your own site, she is it. her tutorials are not free but are not that expensive, and IMO it is money well spent. a few of the intro ones are free to get you started.
for DIY and as-you-go questions, I find https://www.w3schools.com/css/, and https://stackoverflow.com/questions/tagged/css invaluable.
and just generally, keep in mind that there’s always more than one way to approach a layout, so don’t feel you have to incorporate .js or whatever – you might want to, but there’s likely another way.
2 Likes