fog az esze, mint a borotva

Etymology
Literally: “one's mind cuts like a razor”

Verb

 * 1)  to be as sharp as a tack, to be quick-witted

Conjugation

 * For the verb, see.
 * The noun takes the appropriate possessive suffix according to the subject of the sentence:, , , , ,.
 * The rest of the simile remains unchanged.