I had used the Joomla 2.5 and Polish language was available in translation - it was simple.
Now, at 3.5 I could not install the polish language. I had looking for solutions a long time. At the end I opened the Polish language file and I was very surprised(!?) - all the phrases are in the English language.
What happened with the Polish language?

Can you try re-downloading the language pack?

Thank you for your answer :)
I downloaded it again. The same result.
So, I uninstall the component with language obviously. I cleaned all the remnants of k2 on the server (its were not uninstalled in the normal mode).
Just in case, I checked the language settings on the website and on admin panel - I've polish language as default on site, default polish language on admin panel and polish language on "Content: languages".
Once again I downloaded K2 and polish translation (both of links) and installed there.
The same result. I opened the Polish language file - all the phrases are in the English language still.

Does it mean there is no Polish language?

Hello,

I cleared Transifex's cache and the Polish file is working properly now.

Thank you for reporting this.

Yes! It's working :D
Super! Thank you very much :D

Regards :)

You 're welcome Kinga :)