I've insert an new SD card on the device while the device in ON then I can't do anything because the device is freezing.

What I've to do?

You can fix very easy this issue pressing the reset button near the SD card slot. In some cases, insert the SD card while the device in ON may cause temporary freezing of the software and it is a normal behavior. Resetting dont causes data losing except for the last configuration settings done before the reset.