3. If I am offered a Junior Expert job, how fast do I have to be available to leave for the field?

Departure to the field is at the earliest on the first day of the month following the end of the pre-departure briefing.
The exact date of departure depends on the needs in the field, the time needed for administrative procedures (visa request…) and your period of notice. Because of these factors departure can sometimes take place one or two months after the pre-departure briefing ends.