If you ever run into a problem with an iPhone and need to create a video of your screen, you can do that directly with the methods provided by iOS (back to iOS 13).
First, open the Settings application and go the Control Centre. There you find an option for Screen Recording that you can activate:
This adds a recording button to the control centre screen:
To record a video, you click on that button and then a countdown starts. You have 3 seconds to go to the application you want to record and then iOS creates a video of all interactions.
If you want to stop the recording, you click on the red status bar (around the watch) in the left top corner. That will ask you if you want to stop the recording:
It will take a moment until the newly recorded video appears in the Photo app. From there you can share it like any other photo or video.