When i put a issue to "done", how do i open(automatically) the edit option, to put a description ?
You don't. The end of a transition doesn't have any hooks for allowing that.
The closest you can get is to add a transition screen with your description field(s) on it to the transition(s) going into "done". The users will be filling in the field as part of the transition, rather than afterwards, so you still get your data.
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