There’s a LOT to learn! It takes time.
I’ve been playing 8 years, and still have barely touched some areas.
External websites help:
wowhead.com for all about quests and items
icy-veins.com for all about how to build and play classes
If it’s in WoW, it’s on YouTube somewhere.
One thing that I would draw to your attention as a new player, now I notice, is realm choice. Choosing your realm is perhaps the hardest thing for a new player to do, because you have no grasp of how you will want to play the game later, and no understanding of how your realm will affect that.
Realms are all identical in terms of their geography and characters and monsters, but they have different numbers of people, split between Alliance and Horde.
You were directed to Doomhammer by the “New Players” tag. Doomhammer is not specially made for New Players; there’s nothing different about it, it’s just another realm, and Blizzard rotates the New Players tag around them from time to time.
Different realms have different populations, and different ratios of factions.
https://realmpop.com/eu.html shows you the character count by faction on each realm. Look at Silvermoon and Draenor, the most popular realms. Silvermoon is almost all Alliance. Draenor is almost all Horde. There are good reasons for that; it’s better to be on a realm where your faction is in a massive majority. Of course, some people like a quiet game, with few others around, but most people tend to gravitate to “where the action is”, on one of the big realms.
It’s Saturday, so people will be around. If you’re interested in the consequences of this, and have an hour to experiment, make a Human character on Silvermoon realm, get a level or two if you like, and run to the centre of Stormwind. Or make an Orc or Troll on Draenor and run to the centre of Orgrimmar. You might be interested in the difference.
How populated, and which factions, doesn’t matter much when you’re levelling, but once you hit 120, it can make a difference to your joining of guilds and raid teams. It also matters for trade.