Then overlap their photos a little.

Create keyframes at the beginning of the overlap.

Adjust the opacity of the first picture to 100.

The opacity of the second picture is set to 0.

Then create a keyframe where the overlap ends.

Adjust the opacity of the first picture to 0.

The opacity of the second picture is adjusted to 100.

The key to this practice is the location of the two pictures.

Just adjust it yourself.