Chapter 4: I really like the idea!! I hope to read more ;)
You're only 14 and already have a lot of ambition and imagination, that's really great!! You can still improve your writing skills (and I'm sur you will do it) Your stories will be even better then ;D
Well done, I'm looking forward what will happen next in the story ;) See you~
<3

Chapter 3: So after reading these 3 chapters, I have to say, the story idea is very interesting. However, the scientific basis of the story and actual writing is my problem (I swear, I'm only trying to be critical and not mean!!). Mental stress (or pressure, as you call it) cannot cause brain tumors. It can cause other issues such as heart problems, but not brain tumors. As for the writing, the grammar and the word choice makes the story confusing at points. I understand that you are 14 (I started writing at 12 and I had bad grammar at points) and if English isn't your first language (it's not mine either) but try to look up some grammar stuff or have someone who is more skilled read what you wrote and check it for spelling/grammar/any other mistakes. Just writing a little bit clearly and adding more details to create suspense will make your writing better. Even practicing more will let you develop your writing skills. I don't know whether this is your first writing piece or not, but use this as a basis and work on the parts you have problems with.