You don't specify what length of story you are trying to write, but a novel, at full length, is a highly complex piece of work regardless of genre. If you were learning to be a programmer, you probably would not choose to write an enterprise content management system as your first project. You would find it far to complicated, not simply because of its size, but because of all the different elements of software and system design that would be involved in making it all work.
Most writers begin by writing short stories, simply because they are a simpler form that you can get your head around as a beginner.
Now, the short story is an artform in itself, and you may not manage to reach the heights of the great short story writers. But a great short story is something simple done extraordinarily well, and it is the simplicity you want as a beginner.
Short stories may not be the thing you really want to write, and there is certainly very little market for them these days, but the same is true of most of the programs you would write in your early days of learning to code.
Writing short stories will help you learn basic story structures and, perhaps just as importantly, it will teach you to finish things, and show you that you can indeed finish things.
Start with a project of manageable size and complexity. That way you will get to learn the basics and become comfortable with them so that it will be easier to tackle a larger project later on.