If I'm a kid is it ok to write small torture or violence scenes?
I feel like people won't like a story written by a thirteen year old kid if it involves some inappropriate scenes. Response:
I think the bigger possibility is not so much that people won't like your story because of your age but that, if you were writing lengthy or excessively gruesome scenes of violence, the people who care about you might become concerned. They may wonder if you have developed an unhealthy obsession with such topics. Brief scenes that serve the needs of the story are a different matter.
Since I don't know you, I'm going to assume you are a healthy, well-adjusted girl who simply has a passion for writing and wants to be true to her artistic instincts. Sometimes - no, make that all the time - you just have to do what is right for the story you are telling. If it is right, your readers will understand. Those scenes will ring true and they will contribute to the overall meaning of your story.
Writing often involves putting yourself in the shoes of people very unlike yourself, recognizing their feelings, how they see the world, and why they do the things they do - even if they are things well outside your personal experience. Humans have an amazing capacity to do this.
Of course, because I don't know you, the following must be said, just in case. Please forgive me if I sound at all like a parent...
If I'm completely wrong and you actually are developing an obsession with violence beyond that of the average Goth or Emo, perhaps due to a messed up past or personal life, then you obviously need to talk to someone you can trust who has the expertise to support you in dealing with these thoughts.
There's a big difference between imagining a character's perspective and becoming the character so much that you lose sight of yourself.