Q:

Is it possible to write these expressions

Berliners  are nice.
All berliners  are friendly.
All of the berliners help tourists when they need some info.
Are there a lot of differences between these expression on bold

A:

Berliners are nice.

This means Berliners are generally nice people. Of course, the citizens of a large city can't all be nice, but the idea is that most of them are kind-hearted.

All Berliners are friendly.

Although this is claiming that all Berliners are friendly, nobody really believes that millions and millions of people are friendly without exception. So this sentence is basically claiming that the vast majority of Berliners are friendly, perhaps more so than citizens of other cities. It's a stronger way of saying Berliners are friendly. Note: Berliners should always be capitalized, because Berlin is a city and all cities are proper nouns.

All of the Berliners help tourists when they need some info.

This sentence is incorrect when looking at its context. Because of the use of the definite article "the," All of the Berliners means literally every person in Berlin. So the sentence is saying when tourists need info, every single Berliner (i.e., millions of people) will help those tourists.
Instead, I think you want to use All Berliners:

All Berliners help tourists when they need info.

Because all Berliners is indefinite plural, by context it is understood that any Berliner will offer help to tourists who ask for it.

