my iphone 5s lags/hangs

when i play heavy games such as Asphalt 8,Sixguns,gangstar4 and more than my iphone lags

even some times not many a times but sometimes my touch does not work when opening camera app directly through lock screen

battery drainage and

heat up problem are there when i play heavy games and use 3G simultaneously

moreover everytime i go to any authorised service centre they ask for restoring the phone and for heating issue they check the sensors and said they all are ok

but i m not satisfied because phone heats up so high that i can not keep in my hand and play.