Cost of real estate in Przemysl

I have large family apartment in Przemysl, on Legionow str. How can I get approximate value per meter square

Method 1. Check on Otodom the price of comparable apartments and knock off 15 percent. Then divide by number of sqm

Method 2. Find out the typical month rent in Przemysl for that type of apartment. Take 85 percent of that, multiply by 12, then divide by 0.06. Then divide by number of sqm

Thank you for your good suggestion. Shavkat