维修费用是多少？

For a new apartment, where there are only plaster and utilities, you should budget around 1.5 thousand PLN per m2, not including furniture. I'm not sure exactly what you want to do, how things are with the bathroom, kitchen. Depending on how much you leave unchanged, it could even cost you 100 thousand PLN.

Is the apartment from the 90s or earlier? Because if it's from the 90s, the tiles are relatively even, installed on tile adhesive (and not on concrete, as is often the case in many houses...), the electrical wiring is quite new, the water pipes are okay, etc... Removing the tiles, pouring screed, and laying down panels can be done yourself at a low cost (you can fit it in the price of the panels, self-leveling compound, underlays, and an SDS hammer - or hire labor for 10-15 thousand without materials), paint the walls (with the price of paint and tools like rollers and brushes, or labor for 5-10 thousand, depending on quality and speed), and buy furniture (OLX? Local Allegro?). Submit an offer on Oferteo and you will find professionals, so you can choose from different prices.If the block was built before the 90s, then first you need to check a few things: what about the electrical wiring (do you have 2 fuses for the whole apartment, or more - is the fuse box inside the house or in the stairwell, it's worth checking), what are the water pipes made of (plastic, which is easy to replace but has a shorter lifespan, or metal other than copper, which after a long time of use builds up so much limestone that there is a small flow), what is the heating system like (gas, district heating, or a smoky furnace - meaning how much it will cost to replace at the beginning). Check the straightness of the walls and angles on the walls (if straight - just paint; if wavy - either use drywall, or do plastering work, which involves chiseling, applying, and smoothing, etc.). And the floors - are they level, with +/- 1cm between room corners, or so crooked that a ball placed in one room rolls into another (as in concrete block buildings). Floor insulation is important if you live on the ground floor - if you feel cold at your feet, the insulation may be poor, causing significant heat loss. And an important issue is the insulation of the entire building - if it's an "old" unrenovated building, with poor wall insulation, in practice the maintenance costs will be high. Sometimes it's worth insulating "from the inside", if the building management has no plans for external renovations.In conclusion, if you want everything done superbly and exactly as you want it, prepare 50k and don't worry about anything. If you want to save money - do some of the work yourself. If the building is older than the 90s - 50k won't be enough, because there will be many "surprises" - faulty electrical wiring, crooked walls and lack of sharp angles, low water pressure in pipes, 2kg of string around each window and newspapers, tiles glued with magical adhesives (someone glued them onto concrete in my case...), and clogged sewage. You need to first hire a master who will realistically assess what needs to be done, as their opinion will be the lowest cost.

Prepare 60-70 thousand

I suggest that if you have a limited budget, look around on olx. My friend did everything himself and managed to do it for 30,000 zł, but everything was used. Literally everything, even the panels and tiles. A lot of work, but he succeeded.

You should easily fit within a budget of around 50 with labor, unless you come across some scammers

If you spend some time finding perhaps discounted (or second-hand), but still good quality materials, there is a chance to reduce costs. However, the cost of labor will be significant. Professionals are valued, and it's hard to find those with true knowledge and experience. The price may also depend on the location of your apartment. Costs vary significantly depending on the region and location. The issue of furnishing is another point with a wide range of prices. PS. If I were you, Jadwiga, I would seriously consider getting rid of the gas.