Just clear data,clear cache and turn off gallery and use googles photos app until the next official upgrade...
Typing this on the renewed smooth and zippy grand running nb2
Excuse me for not posting screen shots or an official guide... but this fix is fairly very simple
Do tell me if I helped you
After the recent update if ur phone starts lagging go see how much space ur applicatons are occupying. Because due to the recent changes the gallery app is broken nd this causes it to use abnormal amount of space(~14gb which our grand doesnt have) causing the lag issues.. the simplest fix is to just disable the app completely through manage application setting