property

You may approach the civil court.
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Since the matter is already in the Civil Court, I assume that he had filed a suit for the cancellation of the instrument and declaration of right, title, and interest over the said land.
Now, since the matter is already instituted, you can also file a counterclaim seeking the cancellation of his sale deed and alternatively your interest in the property on the ground of adverse possession.

As you have purchased the land some twenty years back along the proper documentation and as currently you are in the physical possession of the same property nothing to worry about........... you can challenge the government if this is the right side then what have you all (GOVERNMENT) approved 20 years before ......put a inquiry into it because as per the rule, even you are followed all the standard operating procedures/ Laws and then only you have obtained the land legally and so regarding the other person who has come up with getting on new demarcation of the land it is is his problem that what the land revenue record officials had marked it 20 years before and now after 20 years that demarcation is changed they will find the solutions themselves...

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ADV. ANISH PALKAR (High Court)

Your defense lies in the doctrine of Adverse Possession. If you have enjoyed possession for 12 years or more, then the land belongs to you.
You can also file counter claim declaring your title to the land through a court of law on the above ground.

Regards
Adv Shreesh Chadha