What's all the legal stuff that should be taken care of and when/how do you go about it?

Sorry if this isn't the right place to post this. I've been banging my head against a wall trying to figure it out and the deeper I go, the more confusing it gets.

I'm a (mostly) solo dev who's been making something for a long time now. I say mostly solo as I'm the main person behind the game I'm making, but I am outsourcing a few things to friends for help.

I don't know how to put this, so I'm just going to get right to the point. The main things I at least want to know are copyrights and trademarks for the game, characters and/or the company.
Is it really necessary to form a studio or an LLC? I get that it's a good idea to do so on the off-chance that you can get sued, but I'm not really made of cash and I don't know if I'd have to keep using it constantly. Is it also really necessary to trademark said studio name and even the game name?

Do I also need to get copyrights/trademarks for my game characters? I want to be able to use them for things outside of games (like art and animation), so if I do need those, would it be best to get them under a studio name or my own name? I also posted a piece of art I made of one of those characters to my social media and a relative advised against it, saying I should get it "patented" so no one can steal it (pretty sure she was confusing patents here). I was under the impression that copyright is made automatically so there's not much need to do that, but I'd be lying if I said I wasn't worried about people essentially stealing my characters.

And finally, I've read that it's a good idea to get proper forms for things like NDAs and asset ownership. Are those also necessary? I already paid a friend for some assets that she helped with. Do I need to get it in writing that I'm allowed to use them?

Given everything that's happening, I'm kinda afraid of moving forward with my game until this stuff gets taken care of or I can at least get some clear answers, so if anyone has any advice, I'm more than willing to hear it. Also, if there's any other legal related things that should be taken care of, please let me know.

I'm in the USA, by the way. It's probably different elsewhere.

Quick edit: At the moment, I am definitely more of a hobbyist, but I am looking to sell the game eventually.

Edit: Typo

 

Get the GameDev Business Handbook. It's a primer for everything you mentioned. Eventually, if you move forward as a business you'll want to talk to a professional. Most areas in the USA have non-profit Small Business Administration offices that can give you free consultation.

 

BTW, this thread reminded me to re-read the GameDev Business Handbook. I had forgotten how good it is. It was funded by Mike Bithell (of Thomas Was Alone, Subsurface Circular, and John Wick Hex), and in addition to the main text by a games business guy, it has advice from devs such as Rami Ismail, too. So it's legit.

 

Is there similar reference for france? Asking for making friend

 

A lot of material is North American-centric, but they try to cover Europe and the UK, too.