(informal) who's to blame? whose fault is it?

Alternative form of la faute à qui

on the alert

(literally) Once a drunkard, always a drunkard; a person who has drunk will drink again / (figuratively) old habits die hard; a leopard cannot change its spots

concerning, as to, as far as ... is concerned

birds of a feather flock together

whoever, anyone / no one, nobody

each one more so than the other, in a trying-to-outdo-each other manner

whoever (in a past sentence)

(informal) practice makes perfect, you'll get better, you learn from your mistakes