40 hours per week is ridiculous. That's a full time job's worth of hours. If you were looking to become a professional then maybe. For mere mortals with limited time and funds twice a week is ample and should see quick improvement.
Also sounds like your car is too quick for you at the moment. I would look into either a slower motor or turning down the settings if your speedo will allow. The key for me is not going too fast too soon. Learn to drive around without crashing first and foremost. The tight lines and corner speed will all come together with practice.
