For dumbs , where can i chance it ?
I just had a look on web and it seems quite easy. Just don't go adjusting all the other settings!!!
From Play store get - 'build.prop Editor' by Nathan Campos.
Open app (takes a few sec to load) and scroll down the build.prop to windowsmgr.max_events-per-sec
Open up this line and change 240 to 150. The prog will create a back-up of your build.prop that you can install.
P.S. Don't go changing other things