Afridi,
You cannot get insurance cover for a few hours only. Actually the choices that you have are not very straightforward. The first thing that you can do is get
learner driver insurance on your friend's car but the minimum cover you can get with that is 4 weeks. You can use the four weeks insurance to get more practice in your friend's car and this is the very best option for drivers with provisional licence.
The second thing that you can do is go with an actual driving instructor. So instead of using the car of your friend, you will be using the car of your driving instructor but the only downside to it is that you will have to take at least a couple of lessons with the tutor for him to allow you to take his learner's car for the practical driving test.