Hi Golom.
After a while I always have the Russian display (russian.png)
If I clean the save folder it works correctly, the next day it's Russian again?
There is no need to delete the save folder every time. There are 3 types of compass. Latin, Cyrillic and Default. When you see the compass on the map, tap it several times and choose the one you like.
Another question: Is it possible to change the "E" to an "O" in the "linear_compass_cockpit_color.png"?
Yes, you need to change the compass image.
The image is in png format. The size is different for each screen resolution. I think I can help you. Write me what screen resolution you use.