See “Practical Advice for Writing a Short Film Script” by Nicole LaJeunesse at videomaker.com:
Short films require a clear focus. The feature film format can support sprawling epics with twisting plots and subplots, but short films are more about capturing a specific moment — there is a lot left unsaid in a short film. You can’t expect to be able to compact a full feature length narrative into a short film format. The plot of your short film, therefore, should be simple and to the point.
Keeping your plot simple will also lead to a more efficient production process overall. If your short film script is easy to produce, you will have more time to carefully compose every shot and do multiple takes to get just the right performance from your actor. In the end, a simple story told well will have a much stronger impact on your audience than a more elaborate story messily crammed into a 5-minute short.