You are a common man and can not fight with anti-social elements and can not proceed in illegal and muscle power.
Contact a local advocate that has taken up the same issue of your father, get certified copies of such orders with other documents that show your possession and legal title and proceed legally.
At least now, construct a compound wall and plant some fruit-bearing trees, as this cost is nominal than fighting in court without risking mental peace.
If you are not able to construct dispose of the plot.
Fortunately, State Govt appointed a commission exclusively for Vizag for such reported atrocities of land grabbing and approach them with a complaint.