I had an offer for a Job in Poland for 8.000 zlotys a month
What city is the job in?
Personally I wouldn't move here for that salary. It's not bad, but it's not great either.
20% of that is taced and your rent will probably be 1000-1500 per month, so you'll have approx 5000zl left, take your travel costs and food from that and you'll have (300 food per week & 150 pertrol per week) and you'll have in and around 3000.
So you'll have less than 1000Euro for yourself per month.
Will that give you a better liftstyle than what you currently have?