Rich person giving bribes and taking lands of others what to do

Sir, my father is an exserviceman when he was doing job at that time he purchased two karnals of land and we constructed house in it and we have done our boundary of our land. The way of our land has some problems with its papers my father has done the taktima of that way but he did not submit its copy in to the patwari and now After some years one man has purchsed the land along with our boundry and now that persob says that my land cones inside of your boundary. Sir plz guide us what we should do because we are very worried that man is very rich he bribes the people and take the lanf of the innocent people by doing some changes.plz guide us what we should because we really don, t know what to do my father is very honest person but now we are in trouble what to do?