Hello,
This is already the case, it works well

There is 0% in the first level Task even if the tasks in second level are almost completed (in the attached example)

It miss a lot of informations:
Did you link children  and parent? Do you work with workload or only with declarative information entered manually the progress? This is normal in this case, the tool does not perform automatic aggregations on manual filling without steering by workload left and done, you have to keep on filling the progress of the parent manually. About workflow if an option is enabled in global parameters, parent can be steered by children's status.

For the little I can see, you don't have work-driven planning.
So progress is not based on real work input.
Only solution to get consolidated progress is use "manual progress" for fixed duration tasks.
Then you have to indicate the weight (or the way the weight is calculated, for instance from validated work) of each tasks.

If a project has 2 tasks, one is at 100% and the other at 0%, what is the progress or the project ?
No it is not 50%. It can be 50% only if tasks have same weight in the project.
If first is DEV and second is TEST, DEV may represent 80% of the project, TEST only 20%.
That why we advise to use Work Driven planning.