"To najszybszy pociąg w Polsce."

Translation: This is the fastest train in Poland.

[Daniel_Draskoczy]

The Warsaw - Berlin express?
Or Warsaw - Krakow maybe?

[Vengir]

More like the latter. The current speed record is 293 km/h, but in regular service not even the fastest Pendolino trains exceed 200. Hopefully with time the infrastructure improves.

[deactivated user]

Perhaps "This train is the fastest in Poland" is also acceptable?

[Jellei]

We really don't like changing the subject of the sentence. And you changed the subject from the dummy pronoun "This" to "This train".

Imagine a situation in which your interlocutor doesn't even know that what you're talking about is a train.

[sergigpas]

Pendolino!

[Joe19902]

Mama mia!