9000 gross per month be ok?
With only three years of experience, it's a long shot, unless you are qualified in some arcane, exotic technology that is highly in demand.
As for living costs, assuming you are a single, non-drinking, non-smoking male in excellent health: and with modest tastes.
One bedroom apartment all inclusive (rent, fees and all monthly bills): 2200 plus in Warsaw, 2000 plus in Krakow and Wroclaw, and somewhat less in other cities.
Food, groceries and household supplies: 1000 PLN, a lot more if you eat out a lot, somewhat less of you can cook simple meals from scratch.
Entertainment and travel: that's a wildcard. Depends on how self-indulgent, lavish and extravagant you are.
Don't forget to include your airfare to and from Poland and the costs of your visa in your calculations, and also about 2000 PLN to set up your apartment. Don't expect to stay longer than a year, two at the most.