how move mouse from external monitors that doesn't touch each other

As your image shows, there is a gap between the built-in display and the two on the sides, so what you are experiencing is to be expected.

The display resolution in your MacBook Pro is not equal to the other three.

You can click the Avanzate... button at the bottom of the window, then turn on the first option (I don't know how it is translated in Italian, probably something like Mostra le risoluzioni come elenco)

and see exactly which resolutions are available.

The closest option is bound to be 1920x1200.

Perhaps if you select 1920x1200 they will all fit tightly together.

(you can't choose 1920x1080 because the internal display has a different aspect ratio, 16:10 instead of 16:9)