In my model Lumia 640 XL files windows 10 mobile app and Whatapp is not working and i am unable to find my SD card. i am unable to turn off my mobile. i have tried to reset the mobile also.has issue with WhatsApp. WhatsApp application crashes after running any video 2, 3 seconds
First check you sd card in other phone, if it is ok then try hard rest your phone. If the problem persists the i think you have damaged your phone's sd card slot or any internal component is damaged. So if don't have professional knowledge about repairing a phone i will not suggest you doing that yourself. Better take it to service center or any good repairing center.