Fullscreen?

[LaMpiR]

Why is it starting in fullscreen and how do I turn it off?

I am loading a .jpg photo with this error, afterwards opens the file normally?

Photo with error:

https://ibb.co/fU4dZH

[xnview]

when you double click on a jpg file from windows explorer, you have this error?
You can change fullscreen in settings>general>Mode when starting...