Probably what you are running into is a virus/malware that has encrypted all your files. You will not be able to view them unless if it is decrypted or recovered.
I would recommend the following:
- install antivirus/anti malware software on your phone and run a scan to delete any unwanted activities. You can find free good software.
- After your system is clean, try to install one of the recovery software such as "Zero Assumption Recovery" or other.
- Try to set auto backup for your important files that you don't want to loose or to get in the hand of cyber criminals.