Robert
Which parts are most important to develop for the car to go faster or is everything equally important?
Well everything is for sure not equal.
Also stats are different depending on the track and when clicking on them in the car tab you can see what each does. But to answer your question acceleration is the most importat, while cooling and reliability are the worst stats to upgrade. There are more advanced concepts for car development but as a beginner this should do the trick, you can also experiment and see what works best for you and what doesn't.
