OK this is a car i heard is suitable for him 2 seats 1.9l and good reliable car if taken car of but my question is camshaft sensor needs to be replaced and brakes and tires and this huge leaks from oil and power steering when you fix all this will the performance be better because now i feel it lacks power how can i fix that?

Its not going to be faster by just fixing the mentioned problems. It will run properly once the cam shaft sensor is replaced but that is more of a tiiming / fuel / air ratio issue. You will also have peace of mind know your son can actually stop the car (brakes and tires) and keep it from leaking all over everyones driveway.