It's hard to look at this question and keep a straight face. First of all, you clearly know nothing, or very little, about programming, so I would recommend spending a lot of time (a couple of years) actually learning a programming language. But before you even do that, I suggest you learn about some actual programming languages, because if you want to make a game like Fortnite, you will almost certainly not use HTML, CSS, and JS (C++ is probably a good place to start). Once you've learnt a language with graphical capabilites well, look at OpenGL or if you really insist on sticking with HTML, CSS, and JS, WebGL. Maybe take a look at Unreal Engine (which uses C++) and/or Unity (which uses C#). Once you've learned how to use those tools (it is definitely an understatement to call them tools), you should find a team of developers (a big team, like a couple hundred developers). Then, finally, you will be able to create Fortnite.
If it wasn't clear, basically, give up. You will probably never create a game like Fortnite. What you can do is create something original of your own. You should always start simple, and since you seem to be completely new to programming, I would suggest trying to make something like a platformer, a maze escape game, or a flappy bird clone (although to be honest, if you're completely new to programming, even that will be pretty hard for you). There is no point in starting a project that you can never finish, especially if you never had the skills required to even start it. Fortnite was developed by Epic Games using their Unreal Engine. It took a massive team of developers (we're talking hundreds of developers) over 6 years to create. You are a single, unexperienced developer...
@MattDESTROYER I am experienced developer and I really know much and I made flappy bird and quiz and I am working in a platformer and etc. I started coding from 3 weeks.
https://flappo.omarhegazy7.repl.co // this is flappy bird
https://quiz.omarhegazy7.repl.co // this is quiz
https://guess-the-number-game.omarhegazy7.repl.co // this is guess the number game
https://startup-of-block-and-red.omarhegazy7.repl.co // this is a game like google dinouser
but thank you so much and also I am not single. I am doing with a friend.
@omarhegazy7 Those are some cool projects, but my point still remains, you don't have experience with 3D games, you've only got one person helping you. My suggestion is you look into Unity and Unreal Engine and try making some 3D games, just experiment. You'll begin to see just how much work it would take to create Fortnite.