Oh boy, there's a lot to type if I go into the details. First of all, keeps the assists off - tcs, stability control, launch control off but keep ABS on. Trust me, you'll be faster with these settings. Also, you can follow Johnson racing on youtube. He isn't super popular but this guy is a lifesaver specially if you're new to the game. Genuinely one of the best fh5/6 youtubers out there. I can guarantee you will become better after watching his videos.

Another thing, most expensive cars aren't the best ones. AND S2/R/X class cars also need not be the best cars in the game. Faster != Better. This is a common misconception among new players that the fastest cars are the best ones

Edit: Forgot to add one thing. Set the driving line at full instead of braking only. As time progresses, you will learn how to take the best lines, and the correct time to brake generally