[Android Central Question]

My Galaxy J7 Prime will not turn off, i have to remove the battery, and then it says "installing system update", then says "no command", then goes to the recovery screen i can move up and down, and can choose, but pressing the power button does nothing, and the phone stays forever in recovery screen.why did I buy this junk???

[Rukbat]

Something (that you did or that happened) corrupted the system. If it happened due to the update, I'd ask the carrier to reflash the phone. (Reflashing wipes all your data, but it's already wiped, so if you don't have a backup, it's gone.) It's possible for an update to do that - it's not common, but I had 2 phones replaced over the years because of it. (I was in the business, so I probably saw more phones in a week than most people see in a lifetime. It's pretty rare for an update to blow.)

If it's not due to the update, reflash the ROM - see [Samsung] How to flash Stock ROM via ODIN. (Have something to do, because if you don't, you're going to spend 10 or 15 minutes watching grass grow - flashing a ROM is the definition of boring.)