As well as the channels Blackheifer suggested if you're looking for advice on mechanics, there's quite a few '5 things to remember for BG3', or 'beginner's guides to BG3'. It doesn't take watching too many of these for the algorithm to recommend more. The rulebooks have gone through a fair bit of changes in 30 years but 5e is well known as being quite newbie friendly.
As well as Wolfheart's youtube channel which does lore videos too if that's what you're looking for both Harbs Narbs and Spell and Shield on youtube do deep dives on particular bits of lore. It would be pretty handy to get a bit of lore about the Dead Three and Shar particularly as they seem relevant.
There are also lots of books in game too that really fill out the lore of the setting
