Had a car accident in which my car was written off. The insurance company paid off the finance and this left me with a small deposit,I had to use some of my own saving to get a new car. I want to know how I can get the money back.

That is the way insurance works. In the event of total loss the settlement covers only your loss, not the cost of buying a new car. You had a vehicle worth "X" fair market value, and insurance gave you and perhaps a lien holder "X" so they are done, there is nothing else to claim.

Cars depreciate in value as soon as they are bought. They gave you the market price for the car. There is no money to come back.

You don't get any more money back. It's over.

You will not get any more money. It is sad but insurance work this way.

Get what money back?

you didn't own the car you crashed in you hadn't paid for it you lost only your deposit