welcome :) If you like some interactive lecture, I started with this one https://tutorial.dyalog.com/ Especially if you don't haver any programming experience. Otherwise I had much fun at the APL Quest which has at least 24 hours of video solving entry level problems.
https://aplwiki.com/wiki/APL_Quest#Problems_from_2016

yes, the latter, thanks!
@LdBeth never have used ¨ that way. It is each with dyadic operand, as described on the help page