[2020] [deleted by user]

As a big ol' lore nerd for this universe, I think there are two good main avenues to start with:

1) I would suggest playing at least some of Guild Wars 1 if you are able to, in particular the Prophecies campaign and the Eye of the North expansion, as those are probably the most relevant to current events (priority after that would be Nightfall campaign since it takes place in Elona, which is where the GW2 expansion Path of Fire takes place). GW1 takes place 250 years before GW2 and adds context and establishes a lot of what exists in GW2: the human gods, dragons, charr-human conflict, etc. The Eye of the North expansion introduces the norn and asura races.

2) I would highly recommend reading the three novels that exist as well: Sea of Sorrows is about Zhaitan (an elder dragon) and the city of Lion's Arch and takes place about 100 years before GW2. Edge of Destiny is about the guild Destiny's Edge, which is made up of characters who show up frequently starting in your personal story and have a large impact on story overall. The events in this book take place a few years before GW2. Ghosts of Ascalon takes place very shortly before GW2 and is about a group of adventurers trying to recover an artifact to strengthen the peace treaty between humans and charr.

After that, the GW2 wiki is a great place to help you fill in gaps in timeline and lore, it's a very easy rabbit hole to go down haha. Other people's suggestions of looking at the overarching lore pages on the wiki are excellent suggestions. You'll also learn a lot by playing the game! Try playing a few different races, exploring maps, and talking to NPCs around the world!