Tickets: Estimated work-time as assigned-time in activity ?

I'm asking for an option to have the estimated ticket-time automatically calculated to the resources assigned time inside the activity

Sorry, I don't understand the request.
Could you please explain ?

OK, I understand now.
In fact it already works as expected except for assigned time.

1. Automatically get assigned worktime for resources in activity (Assignment)

As designed, the project leader tries to "plan" (assign) the work that resources will spend on tickets.
It is important to book time for resources even before we receive tickets, and be sure resource is not booked on other activity.

2. Automatically calculate real and left worktime in activity (Assignment)

It is already working this way (real work entered on ticket is subtracted from left work, initialized from assigned work)

3. Automatically calculate assigned, real, left and resessed worktime in Activity (Costs and work)
It is already working this way

4. Have these worktimes in planning-view, resource-planning, ...
It is already working this way

I guess that what you expect is to initialize assigned from tiket estimated work.
This can possibly be a good idea in use case, but should be correctly designed not to go against existing design.
In your way of working, you plan only what you know.
In designed mode, we try and plan what we don't know yest (but we have information to check is we plannned enough)

When I assign a ticket to an activity, the time is not calculated to activity or project.

How doi you do this.
Do you use Planning Activity ?