Translation:The general secretary puts the documents to the side.
Why "flanken"? How are adverbs changed? Adjectives follow the object - so ... metas la grandaJN dokumentoJN.... but flanken doesn't tell about the documents (and if it did it should have been flankeJN but about "puts" - and why would that get an -n?
Am I all in error here? Some gramar guru, please help :-)
Flanke(n) tells you about the verb and the sentence as a whole.
Adverbs get an -n ending to denote motion just like nouns can following certain prepositions.
Mi iras al la butiko = Mi iras butiken
Exactly. Adjectives (in Esperanto also called a-words) say something about a noun (o-word), and adverbs (e-word) usually say something about a verb, but can also be used for adjectives (a-words).
Li kantas la kanton bele = he sings the song beautifully. (bele says something about "kantas", so about how he sings, not about the song itself)
Li kantas la belan kanton = he sings the beautiful song. (belan says something about "kanton", so about the song, not about the way he sings it.)