I am vainly trying to understand the paragraph below but I am running into some difficulties. In particular, I have a lot of difficulties to figure out exactly what is meant by ダークホース here (there is a comics publisher whose name is Dark Horse but I think it is irrelevant here). The other point is
予測した私は where I am not sure about
who estimates what.
My attempt at translating it:
About this novel.
A certain acquaintance introduced me to the publishing house GAGAGA, they were so much enthusiastic people. They wanted a story polished to perfection. With a distinct accent from Hiroshima, I explained that I tried at best to write in a unique and pleasant style and sought I might success even if at the beginning anybody has any hopes about my work. I slightly failed and sometimes wandered away from the path but here is the novel I wrote.
Here I translated ダークホース by a periphrase explaining that a “dark horse” may well be a horse that has been overlooked in a horse race but will win anyway. The image hinted by the dark horse may be reused by 横道スピン but I did not include it in the translation.