LG G3

Hi guys! :) I have my LG G3 d855 it's android 4.4.2 kitkat and i want it to upgrade to android 5 lollipop, i have watch so many videos and read some threads to upgrade it. The first thing i do is flash twrp d855 2.8.7.0 but the problem is when im booting it into twrp ( Power button and volume up) nothing display it's only black :( . What can i do? help plss :(

P.S my phone is working it's not working only in twrp.