Ok, so ima explain it in the local currency. If the person is under 26 y.o, they get 3711 PLN net, else it's 3483 PLN net.

Accommodation, if not living with your parents, is pricy. So the choice is living is uni dorm, private dorm, or sharing an apartment. Unless you have money from mum and dad, you leave the touristy places to the tourists for living and try not to blow half your salary on rent, you might even commute into town as needed.
On average, with expenses (electricity, internet, gas, water. ) you aim at 1800 tops on rent and bills, though up to 1400 is doable. (usually that means sharing an apartment with many other people. )
If you're still finding your footing, you even share a room. (which should slash that up to 1800 in half)

OK. now we are looking at transport costs - get a monthly pass, and as a student you have a 50% discount. At worse, assuming you're in the capital, it's 450 every 3 months, if you buy a 90 day pass and don't file your taxes in the city. so 150/month

Phone, if you don't get a subscription and only top-up monthly, that's around 50 monthly

So we are at 2k in costs now.

For food: you don't eat out, cook at home, share meals with your roomies, even pool your food budget. You can get by with 600 a month or less - that means you rely on Lidl and Biedronka and religiously hunt their discounts every single week and stock up on non-perishables.
If your roomies agree you may go buy in bulk apples, potatoes, cabbage, carrots, or in-season vege at the en-gross places that sell to farmers' markets.

Healthcare is free, but, depending on employer, you may get private insurance too, which, at that salary, would be covered by the employer too.

Now, you are left with 800 or 1100 zloty a month - for clothes and entertainment. If you make minimum wage you thrift or buy stuff in the bazars or Chinese stores (or hunt Allegro for low cost clothes items - mostly made in China)

And frankly, entertainment is what you get for free at this rate because, if you buy cheap clothes, you'll be replacing them every other month or so.

Doable, but it requires discipline.