My friend transfered a 800MB video file using Files Go to my phone. But due to some error, only half of the file was transfered. Since SD Card acts as default storage on my phone, the video file saved in SD Card. Now when I tried to delete the residual file, it says that it is unable to delete it. Now it shows the same error for any other file as well !! (Stored in SD card not in internal memory). Due to this I can't even send medua files on Whatsapp. What is the problem?
This sounds like it might be a counterfeit, damaged, or faulty SD card. There is no write protect switch on microSD, so the only other thing which might cause a "protect" type message is formatting it on a PC and enabling the optional security features. There are many counterfeit cards out there, the majority of cheap offers (brand names for less than normal) are fakes and junk.