First off, I hope this is coincedentally in the right forum, since I have very little conception of your language, I just guessed. Moderators feel free to move it.
I'm in Sofia right now and the people who would rent me a mountainbike, zigzag tours, couldnt get the mountainbikes ready today. I have only today left, so im looking desperately for a place to rent a mountainbike, but noone in town knows where I could do that. Please let me know if you know something in Sofia or Dragalevci or somewhere else in the neighbourhood of Vitosha mountain.