I don't understand the language in the screenshot but it seems it says "Description is mandatory" so in the field configuration scheme of the issue you have the description as mandatory but the description field is missing from the screen scheme. Thus, this error.
Basically you are making a field mandatory but not adding that field on a screen scheme hence you can't add value to that mandatory field which results in error.
I speak enough French to confirm your guess.
Description is set as a mandatory field, but is not on the "create issue" screen, so can't be set.
Try clicking "Ou est mon champ?" - that will give you an explanation similar to Tarun's, and allow you to click through to where you can change it (if you've got admin rights. If you don't, then contact your admins)
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