Welcome, Jiuwei! 
I hope you find a satisfying life in Azeroth.
I have just a few comments.
I’m sorry to have to tell you that the most urgent is that your account is in danger. Accounts cannot be “gifted”. They are tied to the name, email, and true identity of their original creator, and Blizzard does not allow transfers. In case of question or a need to regain access, you will have to produce ID in the name of the original creator. And you have just posted, on a Blizzard forum, an admission that this account is not yours.
I know that this is an innocent mistake, but at some stage it is possible that Blizzard will nonetheless close this account, since it is not originally yours.
You have put little time into this account so far, I hope. I would hate to put years into developing an account and my relationship to my characters, and then have it yanked out from under me.
I advise you to create a whole new BattleNet account under your own name and email, to avoid living under that threat. You can recreate a few weeks’ progress. I know it’s a loss, but avoids the risk of a greater loss.
Apart from that, as I look at the history of that account,
https://worldofwarcraft.blizzard.com/en-gb/character/eu/argent-dawn/jiuwei/achievements
I see many achievements that you will be cheated of if you continue with it. For example, the Glutton for Punishment achievements. Those are cute and flavorful things that this account has already checked off , but you haven’t. It feels GOOD to earn even the simple achievements, like Duskwood Quests. It feels satisfying. You can never earn these, because your friend’s son already has.
I am sad that that has to be my first message, but I would be remiss if I didn’t explain it.
Ok, whatever you decide about how to continue, we can get on to happier topics now!
WoW is a HUGE game. HUGE. Whatever you are thinking now, it is bigger than that, much bigger. Be gentle with yourself as you learn. Enjoy all the little lessons, and little victories. Don’t be in a hurry to “grow up”. Enjoy the seconds, just fishing or exploring, while you can. There IS a rat-race. A lot of people DO try to keep up with the Joneses. That’s OK. That’s their game. There is also space for yours.
Having said that, it can also be frustrating, especially when you have the wrong idea about something, and are butting your head against things that make no sense. Take help from the Internet. The devs design the game to be played against an external backdrop of players sharing information.
This video is massively long, but broken into 1-2 minute chapters so you can click straight to the subject you are interested in.
https://www.youtube.com/watch?v=zyqj414Se1Y
It will tell you things you didn’t even know you needed to know.
You need to bookmark https://www.wowhead.com/ for anything about quests and items. And ALWAYS read the comments. The comments are the content. They were written by people in the same situation as you when you came to look them up.
There are many more resources on the Net. If it’s in WoW, it’s on YouTube somewhere. AIs can be very helpful - Claude AI, Lumo Ai, Perplexity AI.
Just be aware, with any Internet source, that the game changes, but old posts on the net do not, so sometimes they may give you answers that are out of date. If so, search again for current expansion resources.
Don’t worry so much about being older. Our reflexes and fingers and eyes may not be what they were, but there are many of us in our seventies and beyond who still play. You won’t be chasing any World Firsts, but then, you don’t really want to. The people in the fast lane won’t bother you at all.
Now, about finding RP and people with your interests, I can’t help much with the specifics. I don’t RP. I know Argent Dawn is the place to be for RP, so that’s good. I know that there is also a less bodacious side to the RP communities - cliqueish groups and purity tests and infighting - so you want to steer clear of those when you see them. Become familiar with the Argent Dawn forum to start.
https://eu.forums.blizzard.com/en/wow/c/argent-dawn/190
My biggest piece of advice is: join Discords.
Discord has become the communication network of WoW. There are any number of Discords centred on WoW. Guilds often gave their own. Join many. Lurk. Learn. Ask when you need to. You will have to search, but you will find your people. They are out there.
Here are a couple of Discords you can start with
Wownoob: https://discord.gg/wownoob
https://www.reddit.com/r/wownoob
WoW Porlal Room: https://worldofwarcraft.blizzard.com/en-gb/news/24263355/join-the-adventure-the-wow-portal-room-welcomes-you
There are many more you can find, but I don’t want to overload you. 
Please ask anything else you like here!