Whenever you view photos on the Huawei P20 Pro, it can happen that in full view the images are always rotated automatically.
This can be useful, but it also means that you always have to rotate the phone yourself.
If you don't want to do this, you can deactivate the "Always rotate in full view" function. How this works in detail is explained here:
1. Open the gallery App on the Huawei P20 Pro
2. Then navigate to "More" at the bottom of the menu box and continue to navigate to "Settings"
3. Now tap on "Photo Orientation" and select "System" instead of "Always"
If you now view pictures in full view on the Huawei P20 Pro, they will no longer be rotated automatically.