Alex909

thanks a lot! 
3 days ago I found the 23mm F1.4 R which must be the equivalent of 35mm on Sony, I'm going to try it tomorrow 
Looks like 50mm F1.0 must be used for half car or details to ensure "correct" looking imagines 
Maybe I must buy Fuji 35mm F1.4 to have the most flexible lens for car photography?

Ok, I freely admit my sense of humor stop developing at 12 y/o so I found this funny as hell, even if it was just and accidental mis-spell.

You would be limiting yourself compared to what you should be able to enjoy with a changeable lens body. 
@Edp uses a 75mm as well as many other lenses for his images:
https://www.fuji-x-forum.com/topic/31761-i’ve-found-the-x-t5-to-be-a-capable-camera-for-motor-sports/#comment-99515
As @OzGordo and @Astigmatism mention, try shooting from different distances and find where the lens gives you the pleasing shot for the perspective you want. There are quite a few car - sports shooters using lenses with considerably longer focal lengths to get great shots, as well as wider angles lenses for certain shots.
This link has some more information about perspective distortion:
https://en.wikipedia.org/wiki/Perspective_distortion

It’s not the lens itself, it’s the perspective that changes. A 50mm forces you to move back to get the same field of view so your perspective changes. 

You have changed from a 35mm lens to a 50mm which forces you to change your perspective. Try a 35mm on the XT-4 and your shits should look like they used to. 

The types of distortions that would appear are barrel or pin-cushion distortions, but this shot does not seem to have any. The 35mm is in the “wide-angle” lens group and the 50mm is in the “normal” lens group. Going from the wider to the narrower will give you some lens compression effect, where things look a little more smushed together. That effect is more pronounced going from wide angle to telephoto, i.e. lenses 70mm or longer.
Looking correct is subjective, if you were used to the 50mm - 70mm range, you would probably not have noticed this effect when you changed from the Sony world.

You don't have distortions. Look at the ends of the exhaust pipes, and the wheels on the blue contraptions. They look perfectly circular to me.
If you want the perspective to seem right, you have to view your image from different distances depending on the lens focal length. You want the angle your eye sees between edges of the photo to match the real life angle between edges of the scene. If you do that, even the famous giant nose effect from close up wide angle portraits goes away.

Hello 
I'm Alex from italy
At the moment I have XT-4 with old 23 F1.4 and 50 F1.0