Pay back my excess

On the 3rd of November 2017 I was involved in a car accident with the state car (police van), my car was written off I was told to pay the double access because the state takes too long to pay they gonna refund me once the state has payed them. I have been emailing them for the past four years they are only telling me that the matter is with their lawyers. All I need from them is to pay my excess money with interest.