i don't know this..
i don't know what happens, perhaps i press a button?!?
i can't no more select my polygon or other,
I have a small yellow square at the top left of the screen and I can zoom my selection, but nothing else and i don't know how get out this mode..
please someone can say me what is it?

thank you very much

that just indicate the 2d zoom of the camera and it shows only in View tool, shouldn't interfere with other functionality
so you still should be able to select in select tool (S) or do other stuff in node viewport state (Enter)

to get rid of that yellow square you can reset viewport 2d zoom by clicking on the icon with red circle above your viewport

ok, i try this.
thank you very much.
Bests regards