Real Estate / Buying a restaurant in Poland? [13]

Merged: Buying a restaurant in Warsaw, is it a good deal?

I am foreigner, I have no experience in running a restaurant and I am seriously analizing the idea of buying a restaurant in Warsaw. I think this is a good idea to invest in. I have seen some restaurants but I have not decided yet. The restaurant I would like to buy offers: pizza, kebab and polish food. I am a bit worry about these: the owner of the restaurant said he has been running it for the last 8 years, but he does not have any historical income information he can provide, he said he has other businesses and he is mixing the incomes... so he does not have any specific monhtly paragon fiskalne for the restaurant. (... so no way to see if the restaurant was profitable in the past). I was in the restaurant for few days and it seem that during summer regular number of people visit it, but I have no idea how it will be during the winter.

I would like to have information from all sides to take my final decision.
Thanks a lot for the information you can provide me!.