Help with finding intermediates in the synthesis of Ritalin
In A and B, you should probably draw the C-C single bond in the nitrile longer, it's a bit difficult to see at the moment.
The nitrile is sequentially hydrolysed to an amide and then to an acid.
Treatment with $\ce{ROH/H+}$ is a rather obvious Fischer esterification.




You can arguably work all of this out from first principles: the nitrile carbon is electrophilic, and is therefore susceptible to nucleophilic attack by water. The reaction mechanism is given here. On top of this, the IR peaks strongly support the presence of amide and acid functional groups in D and E respectively.

With that said, I'd argue that there is always going to be an element of "I just know this because I read about it/was taught it before". The very fact that you said "I'm not familiar with the mechanisms/reactions of nitriles" indicates this - if you had happened to read a textbook chapter on nitriles, then you would probably have seen this, since it is one of the most fundamental reactions of nitriles. You would also have to read up about the IR wavenumbers - otherwise it's just gibberish.