ここではタバコを吸ってはいけません。

N5 ここ koko here N5 では dewa then, well, in that case N5 てはいけません te wa ikemasen must not / prohibited

N3 吸 kyuu / su.u suck, imbibe, inhale

N5 〜てはいけない te wa ikenai Indicates prohibition, equivalent to must not do, expresses rule negative obligation or restriction N5 〜ます masu Used at the end of verbs, polite present or future form, makes the sentence more polite N5 〜を o Marks the direct object of an action, appears before the verb, shows what receives the action N5 〜で de Indicates where an action happens, means used, tool, cause, or material depending on context N5 〜は wa Marks the topic of the sentence, indicates what the sentence is about, can contrast with another element, organizes main information