I thought aboutcreating/looking for a Tutorial or something like that for players explaining how game work, or/and for DM, but it should be supper easy, like even spells should be describe with max 30 words or less. Becasue I can see more than often peoples who don't get how this game work, and get think wrong even with spells like armor of agathys.
What do you think ?

The Starter Set is basically a tutorial, but I like the idea of maybe some kind of game store event or something that can teach new players and DMs

D&D Beyond is a digital toolset not really a "learn everything here" kinda site. It offers you tools and the option to buy digital versions of the D&D 5th edition books. This includes the Starter Edition "Lost Mine of Phandelver" campaign.

There are lots of info videos for new players. Try Youtube.

There is a Roll20.net campaign that is always on and active for people to join, chat, help each other learn how to play and features tutorial sessions scheduled once a month.

The Basic Rules set (available here) is all the basic free info you need to play the game as a player or as a DM.

So.. Sure tutorials are great but they already exist by the bucketload, there's starter info here on the site, and therefore not really sure why you're asking if there should be a tutorial when there are many already. Did you not try a search on a search engine or somewhere before making the post?

As Cybermind (sorry I ain't going through all the hoops required to type your handle) pointed out, there are loads of YouTube videos and other primers out there for Dungeons and Dragons.  One I watched recently claimed to get you playing in 5 minutes.  

Dungeons and Dragons by RAW is a complex game.  Yes, it is LESS complex than 3.x and it's successor Pathfinder, but it is still a beast to master.   Those of us that have played lots of games and seen D&D through several iterations often experience times when we know THE rule, but it turns out that 5e has changed it.  Take the Surprised Condition for example, so many players and DMs are still holding on to a Surprise ROUND even though the rules have moved on...but I digress.   D&D being so complex means that you cannot absorb and implement the RAW from the get go.  

Moreover, each player and DM has a role to fulfill in the game and need to devote precious brainpower to mastering that.  For instance, in my home game Players are *required* to know how to implement their spells and class abilities.  I am very, very unlikely to look them up for them and can get a bit testy if say they want to cast a spell and need to read the fine print before doing it.   To me, running a Player Character is the Player's ONE JOB!  New players, of which I have a lot, get it much easier from me, I carefully lead them down the primrose path to utter addiction to my hobby.  The first game is always free.   As my players become more comfortable with their roles and responsibilities, I unveil more and more of the rules to them.   For instance, in my School Club Game, I don't think I ever brought up Inspiration or did I need to explain feats because I forbade Variant Human as a Race and they never reached 4th level.  

You only need to prepare them for what they (the Players) need to know to play the game.  For me, this is mastery of the d20, when to roll it-what to add to it and when and how to tell me the total score, Armor Class, Saving Throws, Hit Points, and How to roll damage with an attack/spell.  Everything else is optional rules in my estimation for new players.  

Cyb3rM1nd I meaned something what can new players and DM can fast referring to, and get easly understand. 
Sure youtube have everykind of video but it doesn't work when you are about fast understand how it work or getting the idea of something. Last time I had to explain my DM how armor of agathys, because he think you can't deal dmg back if attack deal enough dmg to overcome your Temporary hp from spell.
Tutorial sessions, sure it is a thing, but not everyone want to use it for many reasons, and many people would like to fast read how something work in a 2 or 3 sentences, than spending times for tutorial sesions before his own. Yes it is, but not every spell is described or something in 2 or 3 quick sentences, when you are playing caster then it would help out many persons.  Or even spell slot described in book are kinda tricky, myself changing from 3.5 to 5e had to look inside internet to understand how it work, and it took sometime, sure beyond have this quick how to build but its stell walls of text for someone who want to just look at this, not necessary play it. 
And finally everything in 1 place, than looking for everything, not necessary rules but quick explaining and references