The way that the camera rotates with the car as you pan will mean that the front and rear of the car dont have the same movement as you take the shot. The closer you are the more noticable this will be.
If you take the shot as its at 90 degrees to you it will have minimal effect and you can get the sharpest pan but thats not always the best composition!
Keep practicing! I dont add anything in terms of motion blur in post, this one is 1/6th
https://www.robertborowikmedia.com/portfolio/G000079ZKvWEyTgU/I0000G1fxnynYAHY
See how the car is similar level of sharpness front to rear as the car is roughly 90 degrees to the camera.
If the shot was more of a three quarter angle of the car you would see that part that I pan with sharp and the rest increasingly blurry due to the different relative angle and speed of the car in the shot like this one.
https://www.robertborowikmedia.com/portfolio/G000079ZKvWEyTgU/I0000ON_y235x_08
Thats at 1/100th but you can still see how at that angle its not phyically possible to capture the car sharp front to rear, if you see an angle like that with everything sharp its done in post and not in camera.
Just keep shooting for fun!
At 14 you will struggle to find an insurance company willing to insure you for any sort of business insurance, without it a lot of work will be unavailable to you.
For example you can’t take a car out and shoot it somewhere for a restoration company, car sales company etc as your not old enough to drive and you wouldnt have the business insurance to cover you if you damaged it.
You can’t shoot motorsports as you need to be 18 to be trackside and you need £5 or £10 million PLI at most tracks now.
Just enjoy shooting everything, work towards being better all the time and once things will start to fall into place as you get old enough to be able to do these things.