Official Languages in Hong Kong

The Chinese Dialect
Both, Mandarin and Cantonese are difficult to learn, as the way a word is pronounced basis vowel sounds, the difference in brush strokes (simple vs traditional), and characters, can change the meaning and intention of any term or sentence. While Mandarin has four tones, Cantonese has nine.
Cantonese vs Mandarin

Whereas local schools teach Cantonese, all the government and official communication are usually carried out in Mandarin, due to their increased interaction with Mainland China, where Mandarin is preferred and used among other languages in Hong Kong. Both these languages are not mutually comprehensible, which poses a problem, as even though both of them use the same Chinese alphabet, neither of these languages are easy to learn. A person who knows one dialect wouldn’t understand the other lingo due to the complexity of the primary languages in Hong Kong.
Note:
The following interactive Language Map of the languages used in Hong Kong will give you a good idea of the Cantonese speakers in different areas- http://www.ssrc.hku.hk/hklangmaps/
Fact
While English is widespread and commonly used in the Central part of the country, the further you move from there, lesser the number of English speakers you’ll come across.
The English Understanding
Comprehension, fluency, and proficiency in English, in spite of it being the second official language of the country, is not that great, as the natives resort to using Chinese in their common parlance. But even then, it is widely spoken as it is a pre-requisite for many jobs and businesses.