I have more generaly question, how to open company in Poland in the most easy way.Is there are some public institutions which help foreigners in opening company?
You don't need it. However, depending on the locality, they may or may not offer advice. For instance, in Poznan, there's an EU funded NGO that helps people start businesses - and the local Urzad Miasta is very helpful too.
But really, you don't need help - starting a business here is straightforward.