i have lumia 920
an Whatsapp , Viber, Line, almost every app takes so much time to open
i think the problem is from windowss, but not sure!
Did you tried reinstalling the app from windows phone store. Also try a soft reset by holding the volume down +lock button at the same time until your phone vibrates and reboots.
No matter what I try, it's still the same old story. Awkward.
Developers have had a long time to optimise their apps for iOS and Android but have had less time with WP. Also given that companies don't spend as much resources on WP apps, it's no surprise the apps are of worse quality.
IMO this is the real "app gap". The apps exist but often perform poorly and are not updated frequently. But that is progress from not having the apps at all.
