Help me plese, G flex D958 don't go in factory reset topic

I have a big problem with my G Flex D958: my son made a mistake with "guest mode" and i'm not able to return to normal mode. The only thing is to do a factory reset but in guest mode is no possible ( power + volume down don't work, only "download mode" work) like the Lg assistance told to me.
So, i don't have the official .tot file for D958 model ( only for F340k i see), what can i do??please help me!!!:crying::crying::crying: