aight, first off, if you wanna make a track you'll need a lot of free time as it takes a bit to make a track. main things that help: find and replace for file changing, winrar to open the actual file, and the will to learn because theres a lot that goes into tracks.
the way that i do it, i create a new folder in file explorer, then copy a track with a model like atl 15, just copy the zip in mods, then paste in mods and rename it, then open it, take the level folder, put it in the new folder you made, and go in find and replace, change the file to a different name like atlcustom or something, and change the names, then drag the evel folder you put in the file explore folder back into the track file and change the .ter, .terrain, and .png to the exact same as the other files, you can change the track name in the info.json same with authors.
then if everything is done correctly it'll be a new copy of that track, make sure not to delete the .ter, .terrain, and .png, just change the name
and then f11, terrain editor or whatever its called (farthest right option) then flatten the entire track, delete cars, and terrain painter to make it dirt (rocky dirt)
and road decals are spawned through the decal road editor, it tells you in game how to spawn them, but if you dont see it its alt+left mouse click, you can then drag your mouse left/right to make the roads bigger and smaller, the white lines for racing are typically 0.60, it'll spawn as no texture don't worry thats fine, just scroll down on the right side until you see 3 dots and road_invisible, click the dots and search (chaulkline) and thats your racing lines.
to spawn ramps you can use the old world editor and go to art-shapes- and buildings, scroll til ramp_03_somethin idk, spawn it, and then you can manipulate it, make it wider, steeper, etc...., then in the new world editor you go back to terrain edit and allign mesh (it'll have an up arrow and its in terrain editor)
and for table tops typically i use containers because old school, go to art-shapes-misc and its container_01_A and B both work the same, then make wide, taller, etc..., allign mesh and boom, then smooth the sides so they're not complete walls
its self explanatory just go slow until you get a feel for it (its called really smooth in terrain editor)
and you spawn in fps cars through the vehicle selector, select the car you want, move it to the spot you want via wrld editor, and make sure you checkmark (cansave)
if you want color you just make it a color you want via the parts selector and save the car as a preset and boom, you can copy/paste cars, containers, and ramps by selecting them via world editor shift+left mouse click and drag
and if the stadium you're using has a roof, you can either hide mesh or move the model because if you don't, it'll allign the the roof of the stadium and not the ramp,
and to pack the track, go into file explorer or whatever you use, beamng-levels-your track, take everything in that folder and go into the actual track file where you see the .ter, .terrain, etc... and drag everything from the level folder into there and its packed. hope this helps 😄