Hello, @philipp.laengle107
Thanks for your question.
Please allow us to mention that we have tested the rotation of images from the different devices with iOS OS and all images are uploaded in the correct position.
However, we need to mention that it depends on the iPhone default configurations.
Every image file has metadata property. If the metadata specifies the orientation of the image which is generally ignored by other OS, except for iOS and macOS. Most of the images taken are having their metadata property set to the right angle. So iOS shows it 90 degrees rotated manner.
Additionally to all mentioned above, please allow us to provide you with this tutorial, that can be useful for your case:
Macworld
Surprisingly, photo rotation is a complicated issue for software to handle.
In case you will have additional issues with this - please be free to contact me
Also, you can share the link to your application for our testing purposes.
Best regards,