I've learnt it online for a long time, but I'm at the last step of opening it to the game. Any knows how to fix the problem
AC_START_0 and AC_PIT_0 should be there, see https://assettocorsamods.net/threads/build-your-first-track-basic-guide.12/
no those are 3d objects, must be in a ...kn5, again, see https://assettocorsamods.net/threads/build-your-first-track-basic-guide.12/