Sorry, I'm a new immigrant from Shanghai. In daily life in Shanghai, almost all you hear is Shanghai dialect. How to learn Shanghai dialect fastest and most correctly?

Communicating with Shanghainese is the most correct thing. Even if others look down on you a little, you should have the cheek to learn from other Shanghainese. It is generally more likely to ask an older person to tell you.

Like neighbors and colleagues.

I come from Puxi, Shanghai.

If it is Pudong, there may be dialects, which may be different.