あなたはもっと文法を勉強しなくてはいけない。

you (referring to someone of equal or lower status); dear (what a wife calls a husband)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

(some) more; even more; longer; further

grammar; syntax

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

study; diligence; discount; reduction

if ... then; when; and; why don't you...?; the more (one does something); because; since