It's because you don't use "capacity" planning.

You must enter allocated work for resources on each activity.
Then calculate planning.
You'll then have several reports to show how work is planned for resource and its availability.

Yes, but my question is for the project, and project is not on the section work, so it's not possible ?

You can see all projects allocated to the resource in the resource screen.

But this won't tell you is resource still has availability for other project : he may work only 1 day on current project or be full time during whole project duration.
It is the allocated work, spread on days by planning calculation that will tell you this.

ProjeQtOR calculates real "capacity" planning.

My question is : if it's possible to have the number of projects allocated to a Ressource.

For sample : Resource Gabriele has 10 projects allocated

And I don't understand where is the answer to this : Is it possible to see if we can again allocated a project to a Ressouce.

I need your help.

Thank you.

Gabriele Cassano.

My question is : if it's possible to have the number of projects allocated to a Ressource.

On resource screen.

But this is no real information : he may be allocated to 2000 project but work on only one.

And I don't understand where is the answer to this : Is it possible to see if we can again allocated a project to a Ressouce.

Upon which criteria ?

ProjeQtOr does not matter about number of projects allocated to a resource, but to work assigned to the resource.
I think you did not catch the basis of capacity planning.