But firstly, you need to somehow get to know it.
let me throw a theory out at you:
your priest takes you into his office & explains the liturgy to you, in detail.
Or even another theory: the priest does teaching liturgies in the modern language on Saturdays, so people learn, but does the ancient languages on sundays.
Learning the structure of the Liturgy, even including the meaning behind all of its parts, is not a particularly difficult task. But what about all the other services - many of which, for example during Holy Week, that come up only once a year? What about all the hymns and readings of the Epistles and Gospels? You can know the structure of the Liturgy, but alone, it is a form without substance.
Michał Kalina is completely right. I have attended liturgies in languages unknown to me and been able to follow adequately because I know the structure from frequent and, I trust, deepening experience in English. But I have no idea what some of the hymns were - I might guess, as a example, "Troparion for the patron saint", but what would I learn? how would I benefit?