Hello people!
i’m working in a 2d game, i have the demo in offline but the original idea was put the game online.
I’m the only person who work in the game, and i search tutorials for put the game online, like the online of the most played games but it’s impossible to me understand anything about the creation of menu online.
This is my first game and i’m so frustred about this, i need your opinions; its impossible put online a game beeing one person in the work team?
You will automatically understand such stuff, if you gain skills in game development.
If you just started game dev journey, focus first on singleplayer single games / projects.
Touching multiplier at such early stage, will lead you deep into rabbit whole.
Which you probably don’t want to do yet.
Yeah you can make a multiplayer game quite easily, try the free version of Photon, so that it manages it all for you. I do not recommend getting hands dirty with custom networking for a while yet… 
Thanks for the tip, Photon have a guide for set-up?
Yes, in the last time i fallen in a deep hole of videos and guides of youtube and i couldnt make anything good
Yeah it’s a well known solution, probably worth checking their website. I can’t in good faith recommend Unity’s networking at the moment because they’re coming out with a new one and it’s WIP.
So IMHO Photon is what’s best for the time being.
For networking follow what hippo suggests.
For that, you need practice these videos, not just watch them. You wont learn game dev by just watching.