While it has the function "Energy Saving", which lowers the brightness of the screens after a configurable time, I think the ideal would be that the screens can be turned off completely after X minutes of inactivity, when there is no important activity in the telephone (messages, missed calls, voice mailbox, etc.)

This phone, like many quality SIP phones, did not come with a power supply, this is a common practice with SIP phone systems as typically either your phone system already has ports built in, or you have a PoE switch, which I would highly recommend as it is easier to keep a PoE switch on a battery backup keeping your phones up in a power outage