I'm new to mxsim world, i've play demo for month and now i bought the game, playing on other track than rabbithill is freaking hard

And i have issues when i want add some new tracks to the game.
Everything works perfectly when I dl track in .saf. Beautiful track.
But some track than I got, are in a folder with a lot of files. So I put the folder at the same place than .saf, but in game, the track is empty, there is no object

What do I have to do with this tracks ?
Thank you.