Hi.
I used asset manager and set primary assets type to scan in order to be able to load them at runtime but asset manager loads all levels when project starts
I beleive this is the default behavior, you can create your own asset manager class and customize it to your specific needs.
If you havent seen this then it might help:
I cannot find a clear example that shows how to register and load primary assets at runtime. there is only one piece of code showing how they do this in fortnite which is not useful for me.
do you know any straight forward example that clearly shows how I can async load a level at runtime.
thanks. convert your last comment to answer, so I can mark it as resolved 
I’m not sure about this because levels are considered primary and auto loaded. I know you can call Async Load on a primary asset id. Also maybe what your looking for is the asset register & object libraries?
This is about async loading assets:
I have used this to help find assets in the content browser as well:
No problem, you are welcome!