Government Surveyor not measuring the land correctly, he got bribed by the opponent party

We have a land in a district of Bihar. Initially everything was good and we had clear path to our land. Last year we went for treatment in Delhi and it took 2-3 months and we were in the Delhi. And in that period of time few people blocked out path to the land by constructing the 10 feet long wall. And then at first we got land measured by the local surveyor it came out that they have captured the 7 feet of our land front part. Then we approached the government surveyor so that we can file case on the basis of the government surveyor. But when government surveyor came they said they mapped the land with the digital map and said we don't have the path in the front. Then we called the private surveyor and got cross questioned the government surveyor then it again came out that they have captured the 7 feet of our land. But that day government surveyor said that he can't give the report today because he has measured land again so that opponent also gets satisfied.when government surveyor came second time he said that he will map the land with the digital surveyor map. But map is not correct and all other surveyor of my district are not agreeing to give the old. So my question is what I can do to get od map and from where I can get? And what I can do if government surveyor is not honest and got bribed to favor the opponent party.