smart aleck

a smart alec(k) (an annoying self-assertive person who tries to show off how clever they are; a person who is irritating because they behave as if they know everything; a person who thinks they are very clever and likes to show people this in an annoying way; an offensively smart person; a know-it-all) — умник, всезнайка; выскочка, нахал, наглец; прохиндей
Someone who is always trying to make smart, clever, witty or humorous remarks
be a smart-aleck — умничать

...Don’t try to be such a smart Alec and wisecracker. No one thinks it’s clever or funny to keep making smart-assed remarks.

...There’s always some smart Alec or wise guy who likes make wisecracks and dumb comments when someone else is trying his best to save the situation.

smart-alecky —умничающий; развязный и самоуверенный; наглый; нахальный

Synonyms
know-all (informal),
know-it-all (informal),
wise guy (informal),
clever-clogs (informal),
clever Dick (informal),
smarty pants (informal),
smartarse (slang),
smart ass (slang),
smarty boots (informal) ...