I'M having slight difficulty finding someone in Indianapolis who speaks fluent Bulgarian, but I was told Russian is similar. Tutor for English skills needed.
Two languages have shared history where Russian had influence from old Bulgarian, subsequently modern Bulgarian borrowed words from Russian. However, they are very distinct languages. It might be easy for some one to learn the other one if he/she knows at least one of those. Nevertheless, the presumption that some one knowing either of this automatically knows the other one is inaccurate.
I hope this helps.