tonese 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
UPDATE:

Apparently I am wrong as pointed out by a ktard. These words have a direct counterpart in Mandarin, see answer 5.
的 is Dik
嘅 is Ge (correct)

对Is Duii
啱 is ngam (correct)
/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. The 'slangs' are actually found in Mandarin words. It is just that they are rarely used in Mandarin but have more meaning in Canto.
Additional info on corrupted Malaysian Cantonese:

http://www.usj.com.my/bulletin/upload/show...se-is-corrupted]http://www.usj.com.my/bulletin/upload/show...se-is-corrupted

https://chineselanguage.org/forums/viewtopic.php?f=2&t=654

Actually MY Chinese are VERY well respected among PRC Chinese and liked by PRC Chinese.

Prove? Sure:
If u can read the comments
https://www.youtube.com/watch?v=BHmGn6zstW8

Some quotes (There are more):
"我是大陆的，我最喜欢马来西亚华人，超热情的"
https://www.youtube.com/watch?v=BHmGn6zstW8...jcbQKtjp4AaABAg

"出国读书四年了，最喜欢的还是马来西亚华人。在英国读书，感觉白人比香港人更好接触。"
https://www.youtube.com/watch?v=BHmGn6zstW8...VPezVK_V4AaABAg

"好棒的视频。不过在日本旅行的时候，airbnb里遇到的香港小情侣，知道你是大陆人后就不愿搭理你了~~~~房客有美国人+日本房东+台湾人，大家晚上玩回来一起小酌聊天很是开心阿，只有那对香港情侣独来独往............后来在旅行中也遇到过一些香港人，同样知道你是大陆人后就明显变冷淡了，不知为何。反而遇到的马来西亚华人对你异常热情。"
https://www.youtube.com/watch?v=BHmGn6zstW8...RPBtdHEV4AaABAg