Welcome to the Streets of Valhalla. Each specific mission brief is given at the start of every level. Just stay alive - dodge cars and shoot them, dont let anything get in your way. Colliding with cars, and recieving fire from them will result with you losing armor. If your truck has no more armor, its game over.
You can buy upgrades as you advance through the game, using your money. Destroying enemy cars will earn you cash. Some upgrades affect the weight ratio of your truck. You will need strength to balance this. For example, if you wan an object which is labelled with a 3 weight, you will need 3 strength.