[Surface yellowish]

Thanks a lot! You solved my problem 

[Surface yellowish]

Yes it is correct.
It is not only the display of the photos. It is also the same with the colour controls, colour fields etc.

[Surface yellowish]

I am an absolute novice with affinity photo and am taking my first steps with it.
What I find irritating is that the colour white in the photos as well as in the menus is not white but yellowish. When I look at the same photo in PSD, the white area is really white.
I'm sure this can be adjusted, but unfortunately I haven't found out how.