Chosen Solution
In file manager I found “main os” files.. so, deleted the “App Data” or something else. :-P after that every thing gone to blank. at 1st the tiles, then Lock Screen. In panic, I restarted the phone. that’s all.. now my Lumia 640xl only shows the startup windows logo, then it switch off automaticly. what to do now..? then I found some tricks to reboot, using lock key and volume keys combination .. then the bearing screen appeared, after that a sad Emo. it happening again and again.. what to do.?
take a hard reset if not install the Windows Device Recovery Tool just try it hope it helps you
