I know HK follow Chinese script. Well... obviously. Their Cantonese words have direct a counterpart in Mandarin, like 你, is 'ni' in Mandarin and 'nei' in Cantonese. But our Cantonese, we say lei. Why are we so different?

Another example:

的
Mandarin: De
HK: Dik
Local: Gei

对
Mandarin: Dui
HK: Deoi
Local: Ngam

/K answers as simplied below:

1. Influenced by other dialects

2. The words we use are slangs, which HK also use. But we don't know the formal words, which HK knows and use

3. These are 'Lazy' pronunciation, as the language evolved.

4. KL more different from Hongkie. But Ipoh/Sabah closer to HK

5. Diu Lei Lo Mou