In the following, I am using English as an intermediate language to analyze the differences between Hongkongese/Cantonese and Putonghua/Mandarin in terms of their grammar rules and the logic behind them.
１。ready?
Cantonese: 得未can yet／not ready 未得 not-can (yet)
Mandarin: 可以了嗎 can-done-ok-? ／還沒 still-have-not
２。eat a bit more
Cantonese: 食多啲 eat-more-a-bit
Mandarin: 多吃點 more-eat-a-bit
３。If it is like this
Cantonese: (如果)喺咁 (if) is-like-this
Mandarin: (如果) 這樣(的話) (If) this-appearance-as-speak
４。just acting
Cantonese: 做戲咁做 (acting-like-that-do, meaning doing something by acting (superficially and unreal)）
Mandarin: 只不過在演戲 (only-not-exceed-while-acting, meaning like acting)
５。You are crazy
Cantonese: 黐線架你 crazy-?-you
Mandarin: 你有毛病 you-have-(mental)-problems
６。Damn it.
Cantonese: 佢老母丫 his-mother-！
Mandarin: 他媽的 His-mother’s
７。totally wrong
Cantonese: 錯曬 wrong-completely
Mandarin: (完)全錯 all-wrong-or-completely-wrong (can also be 錯光 which is not very common now)
８。Don’t act like this.
Cantonese: 唔好咁 not-good-like-that
Mandarin: 不要這樣 don’t-want-like-this
９。Who
Cantonese: 邊個(人) which-one (person)
Mandarin: 誰 who
１０。Do you support him?
Cantonese: 你支唔支持佢呀？You-support-not-support-him-?
Mandarin: 你支持他嗎？ You-support-him-?
１１。Why?
Cantonese: 點解 how-explain or 做乜 do-what
Mandarin: 為甚麼 because-of-what
１２。How?
Cantonese: 點樣 how-appearance
Mandarin: 如何 like-what
１３ Why? > can’t explain
Cantonese: 冇得解 no-can-explain
Mandarin: 沒甚麼原因 no-whatever-reason
１４。He is a very good person.
Cantonese: 佢好好人 he-very-good-person
Mandarin: 他(的)人很好 He-(His)-person-very-good
１５。please don’t
唔該唔好 not-obligated (but hope you can do it) -not-good (to act)
請不要 ask-for-(as for help)-don’t-want
The above is just a very brief, but interesting, list of the (mainly grammatical) differences between Hongkongese and Putonghua. In fact, the difference between Hongkongese and Putonghua is insurmountable when it comes to the usage of single or combined Chinese characters. Hongkongese is a language on its own, even though both languages use two (significantly different) subsets of a set of dead Chinese characters. What is more intriguing is the Cantonese (significantly) non-Chinese tone system and its usage of a relatively large set of non-Chinese romanizable words with real non-Chinese meanings.
Conclusion: People who use Cantonese/Hongkongese often use very different logic from their Putonghua/Mandarin using counterparts, as far as the usage of the two different languages is concerned. For those who has the preconditioned, but erroneous, beliefs that Hongkongese/Cantonese merely a dialect should reeducate themselves.
This article is prepared for my upcoming youtube video on my http://www.youtube.com/learncatonesefast channel.