der Fortgang
progress
The further development or course of a process, action, or event.
Der Fortgang der Bauarbeiten verzögert sich wegen des schlechten Wetters.
The progress of the construction work is being delayed because of the bad weather.

progress / departure
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progress
The further development or course of a process, action, or event.
Der Fortgang der Bauarbeiten verzögert sich wegen des schlechten Wetters.
The progress of the construction work is being delayed because of the bad weather.

The word is made up of 'fort' (forward, away) and 'Gang' (course, walking/going). This structure explains both meanings: the course of a process (moving forward) and leaving a place (going away).
Wir müssen den Fortgang des Projekts genau überwachen.
We need to monitor the progress of the project closely.
In the meaning 'Verlauf' (course/progress), 'Fortgang' is often used with a genitive or 'von' + dative to specify what is progressing. Typical phrases are 'der Fortgang der Ereignisse' (the course of events), 'den Fortgang der Verhandlungen beobachten' (to observe the progress of the negotiations), or 'über den Fortgang berichten' (to report on the progress).
Die Ministerin informierte sich über den Fortgang der Gespräche.
The minister got an update on the progress of the talks.
The meaning 'das Weggehen' (leaving/going away) is rare today and is mainly used in formal or literary language. In everyday speech, other expressions would usually be used.
Der Roman beschreibt den Fortgang des Helden aus seiner Heimatstadt.
The novel describes the hero's departure from his hometown.
You can recognize the meaning from the context: If it is about an abstract process (work, healing, negotiation), 'Verlauf' (course/progress) is meant. If it is about a person leaving a place, 'Weggehen' (leaving/going away) is meant.
Der Fortgang der Bauarbeiten ist beeindruckend.
The progress of the construction work is impressive.
development
'die Entwicklung' and 'der Fortgang' can both describe the course of a process. 'die Entwicklung' emphasizes change or progress over a certain period of time. 'der Fortgang' is more about how something continues or moves forward, for example a project, an investigation, or a conversation. Learners may confuse the words because both can be used to ask about the status of a process. However, 'Entwicklung' is broader and more common; 'Fortgang' sounds somewhat more formal and is especially suitable when you mean the further course of something.

Beim Termin fragt der Kunde nach dem Fortgang der Reparatur.
At the appointment, the customer asks about the progress of the repair.
Die Entwicklung des Kindes ist für die Ärztin sehr wichtig.
The child's development is very important to the doctor.