Open iMovie on your iPhone
Tap Create Project
Select Movie
Choose the two videos you want to merge
Tap Create Movie
Drag clips to rearrange them if needed
Trim clips if needed
Tap Done
Tap the Share button
Save the merged video to your Photos app
Open iMovie on your iPhone
Tap Create Project
Select Movie
Choose the two videos you want to merge
Tap Create Movie
Drag clips to rearrange them if needed
Trim clips if needed
Tap Done
Tap the Share button
Save the merged video to your Photos app