"there is no car, no people"
ymaps cannot have peds, so that is the way it is supposed to work.
When you use the converter, the props are added to the ymap, but any vehicles, peds and markers will be ignored and not included in it.
To add peds to the game naturally (without using Map Editor or Menyoo), you need to create a scenario and add that to the game separately, outside of the ymap.
ymaps can have vehicles in the form of car generators, but they will not always spawn. It is very random and you will be frustrated. Also, the vehicles will also always be locked, so if you want to set vehicles as personal vehicles and park them by your safehouse, you will always have to steal them to use them, even if they are on your driveway!!. There are no solutions yet to those two problems.
Car generators also cannot be converted automatically to the ymap using the converter. You have to add them separately with Codewalker.