Graceless

This is my first real attempt at writing a book and I just really want to know if there's any potential. I'm not a native English speaker, even though when I'm writing it's the language that comes to me naturally. Still, there must be many mistakes so please try to not to get hang up on those.
I really just want honest opinions about this.
The things that I'm most worried about are the dialogues (I just can't write those spontaneously) and the length of some paragraphs. And, of course, I'm afraid it's just plain boring.
Thanks so much!