mobile

Hello, I decided to join this awesome forum to get assistance into upgrading my L90 to new lollipop. Why? well.. (I'm rooted) days ago I somehow corrupted my google play services and google play store using titanium back up. Sincerely I heard it was very trustworthy but, (of course I had everything backed up) couldn't install them again TB just got stuck for hours installing. So after numerous attempts of restoring order I wasn't able to do so, I decided to do a Factory reset but without luck, and i'm still rooted I don't know why lol. I was thinking of flashing the new lollipop D41520b_00.kdz "official rom" to solve my hard time with the annoying pop up "unfortunately google play store, services also, has stopped working" Im a newbie in this I just managed to root my phone and I don't remember installing any kind of boot-loader or so. I have been reading for hours but I still do not feel confident by myself to do it. So could someone explain me step by step what should I do? I got the .kdz file which is about 1.07 gb

Thank you very much for your time and patience.