It means that people cannot change their bad habits. It is a negative proverb especially for unlovely people.

It means it's impossible to change forever the nature of someone's bad character or habit on the right way. For example:A man like smoking, therefore, we do say 狗改不了吃屎 with negative emotion. It's kind of rude that only be used suitably within close friends and family !

Literally, the proverb means that dogs can't get out of the habit of eating shit.

Thank you, I think I know what it means now. Google translate just translates the last 2 characters as "chi shi" when they are part of a sentence, but if you input them separately you get "eat shit." I guess she is not as crazy about me as I thought...

(諺語 : 負面表達) 比喻惡習不改，劣性難移。 如：「他這個人沒救了！真是狗改不了吃屎！」