Ahoj, najprv skus spravit factory reset, vo vypnutom stave podrz power key+volume down a potvrd 2x stlacenim power key.
Videonavod: https://www.youtube.com/watch?v=D2mqviecS7E

Ak to nepomomze, pouzi LG Flash Tool 2014 a flashni KDZ (obraz originalneho firmware od LG).

LG Flash Tool 2014 stiahnes tu + navod na pouzitie:
https://forum.xda-developers.com/showthread.php?t=2797190

KDZ pre tento mobil tu:
https://forum.xda-developers.com/optimus-l3-l5-l7-l9-ii/development/kdz-stock-firmware-images-lg-optimus-l9-t3592737

Po dokonceni tejto operacie je potrebne znovu spravit factory reset ako som pisal vyssie.