Can you get to the point where if a Polish person met you and didn't know you could think you are Polish?
I would say that's very unlikely. My husband is Polish and says that he's met people who've lived in Poland for twenty years and still don't speak perfect Polish. He says they can be very, very good but never native level, that with the most fluent foreigners, within a few sentences you will know they're not Polish. It's because of the complexity of the grammar I suppose. He says he's never heard anyone who didn't make mistakes. However maybe some Polish members here will have a different opinion?
Now having said that, there are people who pass advanced Polish language exams which rate them as having full competency in Polish, but I don't think that even they will ever 'sound' Polish to a native Pole, anymore than most foreigners will ever pass as English or American or whatever, regardless of how fluent their English is.
can somebody my age if they put in the time get to a good level of Polish or even better.
Absolutely. Your age isn't a factor. You could become quite fluent in a conversational sense, even with imperfect grammar but ideally you need to try to get a balance of skills in reading, writing, listening and speaking. Perhaps studying towards some exams might help you to focus your efforts and it would give you a feeling of being able to measure your progress in definite terms.
I speak fairly basic Polish with loads of terrible grammatical errors but I do manage to make myself understood and can have a conversation with people. My main struggle has always been understanding what people are saying to me. Mowię ale nie rozumiem!
