I have an idea for a novel however I don't know if it is possible as the story line is very controversial and being young I write in a very immature style. This would make the novel very conflicting. I want to know if people think I should try it anyway and edit it later or just make a note of key ideas and write it all at a later date.
Well if your style is immature, only two things will fix that, reading with attention, and writing. Do not neglect the reading with attention part. Francine Prose has a good book called Reading Like a Writer. It will help you learn to read with attention, to understand how the writers you read are actually achieving the effects that make a great story and a compelling read.
As for controversial, truly controversial books don't sell. Pseudo-controversial books sell very well. A pseudo-controversial book is one that picks a fight with group A for the purpose of delighting group B. It is pseudo-controversial because it deliberately pushes group A's buttons, but the real audience for the work is group B who already agrees with it. Because what you are actually doing is picking a fight, you have to present yourself as someone worth fighting with, which is difficult for someone very young. It is generally easier for your opponents to dismiss you are immature than to take the bait and give you the fight you are looking for.
You might be well advised to work on your style for a few years and make sure you really want the fight you propose to pick, and that you are really ready to fight it.
Write your book now, and don't worry about selling it until after it's finished. By the time you finish it, you will be older anyway. And even if you never publish it, it will still be good practice. There's always a good reason not to write any given book at any given time, so sometimes you just have to jump in and write anyway.
If it still seems like a good book idea to you in a few years, you can always rewrite it then. But even if you've moved on from the idea, you'll have learned some valuable things from the process of writing it.
Write it anyway. Most authors have to write a few books before they publish one. Don't think your idea is going to be your one and only idea ever. Some of my published work I have rewritten entire large set-piece scenes over THIRTY times before I liked them.
So you might as well get the first draft out of the way; or at least write your big scenes, if you can write out of order (I do, all the time).
Actually writing it out is a way to "debug" your story and see if you have problems to solve. I often think of this as writing something awful that needs to be fixed! Or I sit down at the keyboard and tell myself, "Okay, let's fail at writing this confrontation." Then afterwards, "Yep, that blows. What is the worst thing wrong with it?"
That may sound weird but it works for me; and it might work for you. Take the pressure off; you aren't writing a masterpiece, you just need something that gives you a direction for research and refinement.