Well, today he explained to me lots of things around pronounciation based on spelling.
For example situations in which "и" is pronounced "ы" depending on spelling, and lots of tips around differentiating between "щ" and "ш" which I find a bit confusing. Last week he told me all about "ъ" which I had misunderstood, for example the difference in pronouonciation of a few words in which ъ is the second letter. I did not know anything about that. He said it would be valuable for me if I memorized all spelling rules.
Really my Russian studies are on hold, but I suppose I could take them up - my colleague inspires me.