According to the LFS Manual, which can be found at https://en.lfsmanual.net/wiki/Cars
XF GTi (XFG) - Front-wheel drive hatchback, similar to sporty hatchbacks such as the Peugeot 106 Rallye/Citroen AX GTi
The main issue is that because you made the layout, and probably did good few laps trying it out, is that you know where the corners are and where they go. For everyone else, it's a case of guesswork and having good memory.
Use the turn and countdown marker boards. These type of boards are used in real tracks, where it's mainly professional race drivers using the tracks, so they're not some sort of 'cheat'.
Corners - very hard to make smooth turn corners. However, for outside of turn, there's no reason why you can't overlap fences, armco, barriers, etc, to get smoother turn ...
Your turn on left; mine on right.
And armco can be overlapped in a straight line. And if you use the Z function, nothing to stop you putting armco above other armco to get higher, and sometimes more realistic barrier.
Other than these (hopefully helpful) hints, the layout was fine
Great to see that you've discovered the Autocross feature, and that you can now make your own layouts
Some feedback on your layout, and on any future layouts.
Do you want to just place objects, or do you want to your layout to look like it would in real life?
In real life, there would be a duty of care, so lots of health & safety considerations.
Normally, you wouldn't start in middle of a street - especially when there's a large car park area nearby. The one to the right of your start point is great - off camber, and you can't quite see the road you have to turn into.
When you have pavements and lamp-posts, why place objects and signs on road, when you can use verges and lamp-posts and street signs?
Use more signs - especially for turns. You designed layout so you know which way to turn. From experience, people just load layout then drive. So therefore get lost, and bit frustrated.
Also, where you have a section where you can build up speed, followed by a turn, best to have countdown markers. It gives warning about big braking needed. Even a single marker is useful.
You were missing a barrier to stop people entering industrial car park on right hand side just before your waypoint.
I would have made spacing between your tyre barriers you used for chicane/slalom a bit bigger. You may have specified using MRT, but people will try other cars, and your chicane is bit tight.