The requested date is just informative : the date the customer requested (his Christmas wish list)
The date that should be taken into account is the validated start date. But it is not a constraint to planning calculation.
You need to set a real constraint to planning calculation. For instance, add a "fixed" milestone starting on tomorrow, then make your first task of project start after the milstone (add dependencing link).

Hello
Thank you for you reply, i understand a little more now 🙂

When i want to plannify my ressource i don't understand but when i put 5 days on my "charge" (#1 in my screenshoot) and i modify the assignation of the ressource and fill 5 days (#2 in my screenshoot) the planning is modify and as you can see (#3 in my screenshoot) there is 7 days of work, howerver i want 5 ?
Can you help me please 🙂

And can you tell how the value in yellow is calculate please in my second screenshoot.

Have a good day 🙂

Have a look at report "planning per resource/project/activity" in "planning" report category.
You'll see exacly what the resource does or is planned to do on the oeriod.
Maybe he is busy on another project.

Hello,Thank for your reply,
Thanks to you i learn a lot of things about the software.

However my problem isn't solve yet.
As you can see in attachment my ressource isn't use in other project so i don't know why the capacity is 6days :'(

Have a good day

Your resource is attending a meeting, on friday, taking 0,06 days of resource availability.
So this resouce cannot work 5 full days on the task you expect him to work. The 5 work days (as workload) will be planned in more that 5 dayxs (exactly 5,06 days, being reported as 6 day (duration is not rounded but ceilled)