update lenovo k3 problem

hello !

i just bought the lenovo k3 note. i have the android 5.0 ... i wanted to check for updates but i cant find anywhere the update button.

i went to setings--about phone and nothing is there,
i tried to force search for updates by dialing *#*#blablabla*#*# and nothing happend.
how is that possible? i cant find anything related to updates in my divice !

please help