With whom and what: the road and company

Everything you need to talk about travelling with someone in Serbian, in one path. Start with the instrumental case - you cannot say I travel by train or I'm going with a friend without it, and the two uses are not the same case doing double duty by accident - then learn thirty words for a travel companion, a reservation, a platform and the rest of what a shared trip needs, walk six guided lessons that take the words into sentences and then break the instrumental into its own short series (building the singular, building the plural, putting both uses to work in a sentence, and the four traps that turn a correct instrumental into a wrong one), read about a solo trip that gains an unplanned companion halfway through, listen to two friends planning a weekend trip on the phone, write about a trip you took with someone and finally practice out loud: read a sentence that puts the instrumental to work twice in one breath.