Need legal advice in adverse possession of a plot

Mai Hazaribag, Jharkhand ka rhne wala hu...mere papa ne 15 saal phle waha ek 4 dismil ka plot kharida tha and galti se 6-6.5 dismil me ghar bna diya. Jis plot par humne galti se construction kar liya wo bhi usi owner ka hai jisse humne ana plot liya tha. 15 saal se kisi ne kuch nhi bola and hume bhi nhi pta tha is bat ka. Land ka previous owner se starting se hamare ache relations the....Uska bhi native wahi tha but kuch dino se wo MP me rhne lga tha. Is beech kai bar hamare ghar aakar milta rha...Lunch kiya but kuch nhi bola. Usne ab ek local aadmi ko power of attorney de diya hai. and last ke 2 months se wo banda aakar hume pareshan kar rha hai. starting me usne current rate se settlement ki bat khi jo ki @current rate (3 lac per dismil) ke according 8-9 lacs ho rha hai. We simply denied this demand and requested him to settle on the previous rate (the rate at which we bought the land). usne clearly mna kar diya and tabse hume tang kar rha hai. My family is modest and we simply don't have that much to pay. My eldest sister is going to be married in coming january and citing this we requested for some time which he declined. We need help in finding solution to this problem as my family is stressed out.