How can I edit the duration of the pics included in my project?

The maximum duration of each photo with no effects applied is 10 seconds. When you apply an effect, then, the duration of the photos might change slightly, as each effect has its own automatic settings. The duration of a video, instead, is usually kept the same as its original one.

After applying an effect, you can change the duration of the photos from theTiming section on the bottom menu (the first icon starting from the right).