You can edit the duration of your layers by trimming them. Trimming your layers will give you control when your layers appear in your movie:

Fig. Trim layers
In order to trim your layer:
- Move your time indicator to the desired spot on the timeline
- Press Alt + [ or Option + [ on the macOS to activate the shortcut to trim your layer
To manually trim your layer:
- Move your time indicator to the desired spot on the timeline.
- Bring your selection tool to the very beginning of the and hover over the start of the layer. You will see the trim layer icon represented by two arrows. (you must see this or your dragging your layers which ...