Hola Franco! You are really good at English, and you only made a few minor mistakes:

Vacation

I'm not so good at writing when the topic is about me. I prefer to invent stories and then publish them.
Yes, I love writing. For some reason, I think writing is a good way to express myself and my feelings.
Since last year I started to write a book which I haven't finished yet. It has around 60 pages. I think while I'm writing I can find out a lot of things that I didn't (past tense because you didnt know then, but you do know now) even know about my own language.
I haven't had enough time to practice my English. Although I'm on "vacation", I have to go to summer school. For some reason I don't get bored when going there.
I think that while I'm busiest I wanna do more things at the same time, it's kinda exciting, but very tiring too.
I'm almost dying right now. I haven't slept so well these days because of the same. I'm doing a lot of things. At least I'm not wasting my "vacation" getting bored at home.
I really wanna improve my English before to I start my classes.

Thanks for your corrections.

No problem! You are doing very well. Just keep practicing, whenever you can :D

My questions are: Which language/s are you learning? - What's the reason why you decided to learn it? - What does motivate you to keep learning and practicing?

Right now I am on break from school for a week, so I too want to get things accomplished. The biggest thing I want to do is practice Spanish. We have Spanish classes at school, but there we do not learn much, so I have to practice at home. I want to learn Spanish because it is fun for me to speak it! :D