I bought this phone in feb this year I bought I cause I was quite impressed with the features it gave at quite impressive price.
Lenovo vibe k4 has 3gb of ram and 1.3ghz octa-core processor so there is no sign of lagging when we use it normally.
But when we go for high graphics gaming it starts to lag but its not a big problem we can ply the same game with medium graphics then there wont be any lagging and no heating problem also.
Coming to the camera it has 13mp front cam and a 5mp rear cam and the image quality is satisfactory we can get good photos even at low light because of the dual flash.
About visuals and sound no one can beat it in sound quality it has Dolby atmos what more we need and supports 1920p so we can have a great visual and sound experience on this device and it supports fast charging phone charges till 60 in 45 mins. so all in all this is a good phone to buy at 13000.