I tried to play with my Xbox controller but the car's steering is too fast, how can I fix this?

steer slower

Try increasing "Steer centre reduction" in Options-->Controls. This will slow the steering wheel when it's close to centre but it will become even more twitchy at large steering angles. play arund with this setting.

Maybe someone whos using a joystick will be able to help more

You can decrease the steering lock in the setup.

or you can do what i used to do and make the axis ranger longer than it usually is.
The default values for it is -1000 to 1000 iirc

so you can do -1500 to 1500 or -500 to 500 depending on what you're looking for.

Option/Misc/Analogue Steer Smooth

The best is just to reduce car steering lock in car setup in garage. Start off by reducing by 50% and see from there where is the sweat spot that allows for best balance of manuveability vsrsus steering precision. For XFG on BL1 you may even go down to 12deg and still be able to complete a lap without any issues, just pit exit will be somewhat tricky.