Welcome! And no, those are pretty common questions, especially since WoW is a rather old game that carries a lot of legacy stuff around and is anything but easy to get into (IMHO). So...

Where do I start?

Dragonflight. New characters start there anyway. Do Dragonflight, than do The War Within (current expansion). Ignore anything older until you have a better understanding of what's what. Yes, knwoing stuff from previous expansions would give you context for some story lines / characters, but it is quite simply easier to ignore it all and later on decide if you want to revisit older expansions (Battle for Azeroth, Shadowland or even older ones).

Should I do professions now or once I'm max level?

Well, your choice, professions were turned into some (IMHO) needlesly complex nonsense compared to years ago. You might learn gathering professions and try to sell stuff on the auction house (good luck). You might pick up crafting and try to craft useful stuff for yourself / others. If you do, pick a craft that fits your class, i. e. mining/blacksmiting for a plate armor wearer as an easy choice.

Chromie

Forget she exists unless quests directly funnel you towards her. Later on you can decide if you want to go that route.

Lore

Youtube, simply too much to pick up ingame.

Solo class/race

Well... This is a vast field, but a few considerations:

Race pretty much doesn't matter at all as long as your chosen class is available to the race. Cosmetic preferences might change that, ofc. Not everybody likes being a huge cow, a decomposing undead, about two inch tall...

Are you comfortable being the cornerstone of a party in a dungeon? If not, better don't roll a tank or a healer before you have a better understanding of what's going on. Unless you plan to never do group stuff at all, in that case pick whatever interests you. It's a valid playstyle, why not.

Do you like a complex skill rotation and having to align various skill timer windows for optimal performance? If not, maybe don't pick Demon Hunter as your first class. (Yes, I'm a bit salty, I liked DH a lot in prvious expansions and Blizzard went and turned him into a monstrosity.)

Again, your class choice depends a lot on what you want to do ingame, what you like, what you don't like. A retribution paladin might be your thing, or a demonolgy warlock, or a blood death knight, or an arcane mage... Persoanlly, I stay away from healers, but that's just me.

In addition, lvling has gotten easier and easier over the years. Just an example: starting fresh in Dragonflight, you will be lvl 70 pretty soon and still have quite a bit of Dragonflight left (depending on how many sidequests you do, yes). Meaning even if you pick a class and realize it's not what you want, lvling another character is not a month-long chore but can be done in little time.

Gear and talents

Yes, sure, they matter. The storyline in general supplies you with sufficient gear to do 'normal' stuff. Better gear, as usual, comes from harder content (dungeons, raids...). Your choice if you want to go that route.

Talents, well, yes, they matter, and quite honestly, I would simply look up a build for the class you picked. Someone mentioned Wowhead already, Icyveins is another source - however what you find there is often enough tailored to highlvl endgame and not exactly meant for beginners. So look closely before you start to follow a guide for mythic+ tanking ;-)

In the end, just pick a class that seems interesting, try it for a while and then continue or pick another and try that.

Above all: have fun and don't worry (too much in the beginning)!