Why Hong Kong ppl so rude?

In restaurant everyone shout at the top of their voice

Order food ask to hurry up when I inquire about the dish

Then throw the dish on table

Their life is fast paced but in Japan also fast paced yet polite

Can hear shouting
Lei GAO Chor ah???
Chi seen
Lei ho mo ah??

Worst is they are rude coz i don't speak Cantonese
Speak mandrin they think I'm PRC so then I speak in English but they don't understand?

They think I'm PRC??? How

I was in Shanghai, the pace there is pretty fast too.
But the people there are nowhere near to hongkies rudeness. All my encounter with shanghainese were very pleasant. They got even more friendly when they found out I'm Malaysian.

The only friendly hongkie i met is actually a Singaporean, been doing business there for years.