You can print the screen using buttons CTRL + PRTSC
Now you have to open a graphic editor like paint or something like that.
In paint click on new file/picture and then use buttons CTRL + V in order to past the printed screen.
I want that the small preview of the pictures and it names shall fill the entire screen I am watching. So everything in top, button and to the left should be hidden until I want to see the view over the other folders on my left
Saying "small preview" I mean where you can see what picture your are looking at without opening it to a bigger size