Before diving into firmware, it is essential to understand the hardware. The LM-K500UM is typically a high-brightness, ruggedized TFT-LCD module used in:

Firmwares * LG K41S K410HM. K410HM20a_00_OPEN_SCA_OP_1223.kdz. * LG K51 K500MM. K500MM20f_00_MPCS_US_OP_1030.kdz. * LG K51 K500MM. LG-Firmwares.com LG-Firmwares.com: LG phones fan club

: If your K51 is lagging, a clean firmware reinstall (often called a "factory flash") can remove corrupt system files that a standard factory reset might miss. How to Check Your Current Version Open Settings . Navigate to System > About Phone .